swint argued january decided april together steelworkers america et al swint et also certiorari respondent black employees brought suit federal district petitioners employer certain unions alleging title vii civil rights act violated seniority system maintained petitioners district found differences terms conditions privileges employment resulting seniority system result intention discriminate race color held therefore system satisfied requirements act section provides shall unlawful employment practice employer apply different compensation standards different terms conditions privileges employment pursuant bona fide seniority system provided differences result intention discriminate race appeals reversed holding differences treatment employees seniority system resulted intent discriminate thus violated although recognizing federal rule civil procedure requires district findings fact set aside unless clearly erroneous appeals concluded finding discrimination nondiscrimination finding ultimate fact review making independent determination allegations discrimination though bound findings subsidiary fact clearly erroneous held appeals erred course review district judgment pp showing disparate impact alone insufficient invalidate seniority system even though result may perpetuate discrimination absent discriminatory purpose operation seniority system unlawful employment practice even system discriminatory consequences pp rule divide findings fact deal ultimate deal subsidiary facts rule apply conclusions law district faulted applying erroneous definition intentional discrimination rather reversed arriving appeals thought erroneous finding whether differential impact seniority system reflected intent discriminate account race purposes question pure question fact subject rule standard discriminatory intent means actual motive legal presumption drawn factual showing something less actual motive thus appeals may reverse district finding discriminatory intent concludes finding clearly erroneous rule pp appeals correctly stated controlling standard rule conclusion challenged seniority system unprotected product improper independent consideration totality circumstances found record appeals concluded district erred failing consider certain relevant evidence improperly made determination based evidence district finding discriminatory intent set aside error law appeals relieved usual requirement remanding proceedings tribunal charged task factfinding first instance pp white delivered opinion burger brennan powell rehnquist joined stevens filed statement concurring part post marshall filed dissenting opinion blackmun joined except part post michael gottesman argued cause petitioners briefs petitioners robert weinberg laurence gold jerome cooper bernard kleiman carl frankel samuel burr stelzenmuller filed briefs petitioner elaine jones argued cause respondents brief jack greenberg james nabrit iii patrick patterson judith reed barry goldstein lani fn solicitor general lee assistant attorney general reynolds deputy solicitor general wallace jessica dunsay silver marie klimesz constance dupre philip sklover vella fink filed brief et al amici curiae urging affirmance robert williams douglas mcdowell filed brief equal employment advisory council amicus curiae justice white delivered opinion respondents black employees bessemer plant petitioner company manufacturer railway freight cars parts brought suit company union petitioners steelworkers america local collectively usw alleging violations title vii civil rights act stat amended et seq ed supp iv come cases involve validity title vii seniority system maintained company usw district found differences terms conditions privileges employment resulting seniority system result intention discriminate race color app pet cert hereinafter app held therefore system satisfied requirements act appeals fifth circuit reversed find differences terms conditions standards employment black workers white workers resulted intent discriminate race hold system legally valid section title vii title vii broad remedial measure designed assure equality employment opportunities mcdonnell douglas green act designed bar overt employment discrimination also practices fair form discriminatory operation griggs duke power thus repeatedly held prima facie title vii violation may established policies practices neutral face intent nonetheless discriminate effect particular group teamsters hereinafter teamsters act treatment seniority systems however establishes exception general principles section stat set forth provides pertinent part notwithstanding provision subchapter shall unlawful employment practice employer apply different standards compensation different terms conditions privileges employment pursuant bona fide seniority system provided differences result intention discriminate race precisely happened cases following decision teamsters district held new trial limited question whether seniority system instituted maintained contrary section new civil rights act app concluded noted discuss system adopted maintained purposes wholly independent discriminatory intent appeals fifth circuit reversed ii petitioners submit appeals failed comply command rule findings fact district may set aside unless clearly erroneous first describe findings district appeals certain facts common ground district appeals company bessemer plant unionized early unionization plant divided number different operational departments usw sought represent production maintenance employees plant elected bargaining representative bargaining unit consisting employees time iam became bargaining representative unit consisting five departments iam ceded certain workers bargaining unit usw result transfer iam bargaining unit became white throughout period representation usw plant approximately half black prior company openly pursued racially discriminatory policy job assignments departments contained one job category result departments racially mixed lines progression promotion within departments seniority system issue adopted agreement seniority measured length continuous service particular department seniority originally exercised purposes layoffs hirings within particular departments seniority formally recognized promotional purposes well however seniority limited exceptions exercised within departments employees transferring new departments forfeited seniority seniority system remained virtually unchanged suit brought district approached question discriminatory intent manner suggested fifth circuit james stockham valves fittings appeals stated teamsters totality circumstances development maintenance system relevant examining issue view however four particular factors focus first must determine whether system operates discourage employees equally transferring seniority units ibid district held system facially neutral applied equally races ethnic groups app although charges racial discrimination application held substantiated evidence concluded system applied equally uniformly employees black white given approximately equal number employees two groups quantitatively neutral well second must examine rationality departmental structure upon seniority system relies light general industry practice james supra district found linking seniority departmental age modal form agreements generally well manufacturers railroad equipment particular app furthermore found basic arrangement departments plant rationally related nature work consistent practices generally followed unionized plants throughout country questions raised necessity certain departmental divisions found challenged lines division grew historical circumstances plant unrelated racial discrimination although unionization produce iam bargaining unit found usw charged racial bias response iam situation usw sought represent workers black white plant company charged racial discrimination may existed iam company properly took approach towards establishment election units bargained unions afforded representational status nlrb without discriminatory animus seniority system genesis period racial segregation certainly practiced system product bias system rather came result colorblind objectives union unlike structures institutions era arm segregated society foster discrimination practiced custom plant app appeals addressed four factors james test reached opposite conclusion first held district erred putting aside qualitative differences departments blacks concentrated dominated whites considering whether system applied equally whites blacks purported correction legal standard evidence evaluated second rejected district conclusion structure departments rational line industry practice reflect discriminatory intent discussion brief focuses role iam certain characteristics unique bessemer plant concluded record evidence generally indicates arbitrary creation departments company since unionization attendant adverse affect sic black workers individual differences departmental structure plants compared industry practice indicative attempts maintain departments third considering genesis system appeals held district erred holding motives iam relevant correction legal error part district excluding relevant evidence stop however went hold iam acting discriminatory intent issue specifically reached district considerations race permeated negotiation adoption seniority system subsequent negotiations thereafter ibid fourth despite conclusion third james factor appeals recited expressly set aside find clearly erroneous district findings respect negotiation maintenance seniority system announced aving carefully reviewed evidence offered show whether departmental seniority system present case bona fide within meaning title vii reject district finding elaborating disagreement appeals stated analysis totality facts circumstances surrounding creation continuance departmental system leaves us definite firm conviction mistake made doubt based upon record case existence discriminatory purpose obvious principal aim exclude black workers bargaining unit goal ultimately reached maneuvers resulted unit interest increased membership acquiesced discrimination succeeding significantly segregating departments within unit district might reached different conclusion given role creation establishment seniority system due consideration ibid omitted consider significant decision manner two seniority units set creation various departments within unit time certification years thereafter conditions racial discrimination affected negotiation renegotiation system extent system attendant rule locked blacks least remunerative positions within company find differences terms conditions standards employment black workers white workers resulted intent discriminate race hold system legally valid section title vii although discrimination vel non essentially question fact time ultimate issue resolution case expressly proscribed finding discrimination finding ultimate fact cites omitted reviewing district findings therefore proceed make independent determination appellant allegations discrimination though bound findings subsidiary fact clearly erroneous iii pointing statement appeals similar statements title vii cases coming petitioners submit appeals made independent determination discriminatory purpose ultimate fact case error rule agree petitioners appeals followed seems accepted rule circuit judgment must reversed rule broadly requires findings fact set aside unless clearly erroneous make exceptions purport exclude certain categories factual findings obligation appeals accept district findings unless clearly erroneous divide facts categories particular divide findings fact deal ultimate deal subsidiary facts rule apply conclusions law appeals therefore quite right saying district findings rest erroneous view law may set aside basis district faulted misunderstanding applying erroneous definition intentional discrimination reversed arriving appeals thought erroneous finding whether differential impact seniority system reflected intent discriminate account race question see pure question fact subject rule standard question law mixed question law fact previously noted vexing nature distinction questions fact questions law see baumgartner rule furnish particular guidance respect distinguishing law fact yet know rule principle unerringly distinguish factual finding legal conclusion reasons follow however little doubt factual nature requirement seniority system free intent discriminate treating issues intent factual matters trier fact commonplace dayton board education brinkman principal question whether defendants intentionally maintained racially segregated school system specified time past recognized issue essentially factual subject rule commissioner duberstein held principal criterion identifying gift applicable provision internal revenue code intent motive donor one inquires basic reason conduct fact resolution issue determined ultimate issue whether gift made issues held questions fact subject rule yellow cab antitrust case referred indings design motive intent men act peculiarly factual issues trier fact therefore subject appellate review rule justice black dissent yellow cab suggested contrary approach relying griffith argued always necessary prove specific intent restrain trade enough restraint result consequence defendant conduct business arrangements approach however specifically precluded title vii cases challenging seniority systems differentials among employees result seniority system unlawful employment practices unless product intent discriminate make sense therefore say intent discriminate required may presumed impact construed teamsters must finding actual intent discriminate racial grounds part negotiated maintained system finding appears us pure question fact say discriminatory impact part evidence considered trial reaching finding whether discriminatory intent factual matter assert however discriminatory intent finding fact made trial question law mixed question law fact kind cases may allow appellate review facts see satisfy legal concept discriminatory intent discriminatory intent means actual motive legal presumption drawn factual showing something less actual motive thus appeals may reverse district finding discriminatory intent concludes finding clearly erroneous rule insofar fifth circuit assumed otherwise erred iv respondents directly defend fifth circuit rule trial finding discriminatory intent subject standard rule rather among things submit appeals recognized appropriate properly applied rule setting aside findings district position force two reasons persuasive first although appeals acknowledged correctly stated controlling standard rule acknowledgment came late opinion expressly referred applied rule course disagreeing district resolution factual issues deemed relevant james stockham valves fittings furthermore paragraph finally concludes usw seniority system unprotected strongly suggests outcome product independent consideration totality circumstances found record second fundamentally stated convinced mistake made identified mistake also source mistake mistake district record doubt existence discriminatory purpose source mistake district failure recognize relevance racial purposes iam district given role creation establishment seniority system due consideration might reached different conclusion supra appellate discerns district failed make finding erroneous view law usual rule remand proceedings permit trial make missing findings actfinding basic responsibility district courts rather appellate courts appeals resolved first instance factual dispute considered district demarco proceeding manner seems us incredible unless appeals construed circuit rule respect authority arrive independent findings ultimate facts free strictures rule also permit examine record make independent findings respect issues district findings set aside error law previously said however premise conclusion infirm whether ultimate fact discriminatory intent factual matter subject standard rule follows district finding ultimate fact set aside error law appeals relieved usual requirement remanding proceedings tribunal charged task factfinding first instance accordingly judgment appeals reversed cases remanded proceedings consistent opinion ordered footnotes procedural history cases rather complex original complaint filed since time case tried three times twice reviewed appeals prior unionization bessemer plant divided departments departments usw units international association machinists aerospace workers iam units departments remained essentially unchanged international brotherhood electrical workers ibew gained representation status two small departments ibew unit white ibew however decertified members reabsorbed department represented usw departmental seniority system part initial agreement company usw however seniority system changed one based departments one based upon particular occupations within departments system went back departmental base exceptions see infra employees transferring request company electing transfer lieu layoff company entered agreement department labor bring employment practices compliance executive order cfr provided exception departmental limit seniority allowing certain black employees make interdepartmental transfers without loss seniority fifth circuit relied upon following passage teamsters seniority system litigation entirely bona fide applies equally races ethnic groups extent locks employees jobs placing line drivers separate bargaining unit employees rational accord industry practice consistent national labor relation board precedents conceded seniority system genesis racial discrimination negotiated maintained free illegal purpose specifically declined make finding whether provision seniority system greater relative effect blacks whites qualitative differences departments concentrated believed inquiry inconsistent earlier fifth circuit opinion case particular focused history unionization process plant found certain departmental divisions based evolving relationship usw iam respect usw district found nion meetings conducted different sides hall white black members social functions union also segregated app also found however hile possessing trappings taken otherwise segregated society usw local one institutions area function fact foster maintain segregation rather served joint interest white black workers higher priority racial considerations appear us district actually found qualitative difference held irrelevant relevant passage district opinion read follows ranking usw iam departments according perceived order desirability one attempt measure relative effect rule white black employees may well somewhat greater impact felt blacks whites although conclusion means certain original complaint case mention iam prior first trial respondents sought received leave amend complaint add iam rule defendant insofar relief requested may involve infringe upon provisions union collective bargaining agreement company order district june app gypsum characterized standard follows finding clearly erroneous although evidence support reviewing entire evidence left definite firm conviction mistake committed note appeals quoted passage conclusion analysis district opinion supra see jackson city killeen payne mclemore wholesale retail stores wilkins university houston lindsey mississippi research development center rohde steel castings joshi florida state university phillips joint legislative committee danner civil service thompson leland police crawford western electric burdine texas dept community affairs williams tallahassee motors parson kaiser aluminum chemical causey ford motor east romine indication opinions appeals fifth circuit see supra circuit rule respect ultimate facts another way stating standard review respect mixed questions law fact ultimate fact statutory legally determinative consideration intentional discrimination satisfied subsidiary facts admitted found trier fact indicated text however question intentional discrimination pure question fact furthermore appeals opinion case appears address issue question fact unmixed legal considerations time occasion indicated findings ultimate facts independently reviewable baumgartner issue whether findings two lower courts satisfied standard proof necessary sustain denaturalization decree held conclusion two lower courts exacting standard proof satisfied unreviewable finding fact one reviewing independently assess referred finding one ultimate fact case involved appraisal strength entire body evidence said significance proof standard lost ascertainment lower courts whether exacting standard proof satisfied whole record deemed fact order facts open review fifth circuit rule appellate consideration ultimate facts roots discussion baumgartner galena oaks scofield question whether gain derived sale number houses treated capital gain ordinary income appeals relied directly baumgartner holding issue ultimate fact appellate may review free rule causey ford motor supra relying galena oaks scofield supra said although discrimination vel non essentially question fact time ultimate issue resolution case deemed independently reviewable passage east romine supra repeated cases us supra rested opinion causey ford motor whatever baumgartner may meant discussion ultimate facts surely mean whenever result case turns factual findings appellate need remain within constraints rule baumgartner discussion ultimate facts referred pure findings fact find discriminatory intent context findings clearly impl application standards law noted appeals certain points purport correct viewed legal errors part district presence legal errors may justify remand appeals district additional factfinding correct legal standard infra see furnco construction waters proof employer work force racially balanced contained disproportionately high percentage minority employees wholly irrelevant issue intent issue yet decided need therefore address issue applicability rule standard mixed questions law fact questions historical facts admitted established rule law undisputed issue whether facts satisfy statutory standard put another way whether rule law applied established facts violated substantial authority circuits sides question compare ex rel johnson johnson stafos jarvis johnson salisbury rogers bates pennsylvania casualty mccoy also support decisions proposition conclusions mixed questions law fact independently reviewable appellate bogardus commissioner helvering oil helvering rankin commissioner duberstein commissioner heininger neither dissent contend rule inapplicable findings discriminatory intent rather contends rule properly applied appeals particular regard second james factor whether departmental structure rational line industry practice appeals focus evidentiary basis particular finding district appeared make independent examination record arrive conclusion contrary district likewise dealing genesis seniority system whether negotiation maintenance system tainted racial discrimination appeals identifying thought legal error failing consider racial practices intentions iam otherwise overturn district findings clearly erroneous see moore lucas moore federal practice trial fails make findings find material issue appeal taken appellate normally vacate judgment remand action appropriate findings made rule international assn bridge workers chicano police officer assn stover gresham burch international assn machinists aerospace workers general electric credit robbins iam discriminatory motivation existed imputed usw relevant extent may shed light purpose usw company creating maintaining separate seniority system issue cases discriminatory intent part iam therefore control outcome cases neither fact true usw acquiesced racially discriminatory conduct part iam acquiescence equivalent discriminatory purpose part usw justice stevens concurring part except extent preliminary comments burden sustaining challenge seniority system title vii ante inconsistent views expressed separately american tobacco patterson ante join opinion justice marshall justice blackmun joins except part dissenting group negro employees bessemer plant brought class action steelworkers america local usw international association machinists local iam plaintiffs alleged inter alia departmental seniority system negotiated unions discriminated negroes violation title vii civil rights act et seq ed supp iv civil rights act district northern district alabama concluded seniority system operate discriminate negroes unanimous panel fifth circuit reversed ruled district committed several errors law including failure give proper weight role iam relied patently inaccurate factual conclusions swint remand district ruled seniority system immune attack title vii time finding respondents failed show discriminatory intent required decision teamsters ante fifth circuit unanimously rejected conclusion district majority reverses fifth circuit second unanimous decision ground appeals pay sufficient homage clearly erroneous rule fed rule civ proc concluding seniority system product intentional discrimination negroes agree premise majority decision remand cases yet another trial application premise facts case respectfully dissent majority premises holding assumption absent discriminatory purpose operation seniority system unlawful employment practice even system discriminatory consequences ante quoting trans world airlines hardison previously indicated find anything relevant statutory language legislative history support proposition title vii immunizes seniority system perpetuates past discrimination system issue clearly simply plaintiffs unable demonstrate satisfaction system adopted maintained invidious purpose see teamsters supra opinion marshall opinion placing burden plaintiffs challenge seniority systems admitted discriminatory impact burden never imposed civil suits brought title vii frustrates clearly expressed congress effectively freeze entire generation negro employees discriminatory patterns existed act quarles philip morris supp ed butzner ii even accept decision impose novel burden title vii plaintiffs still unable concur conclusion fifth circuit decision reversed failing abide rule majority asserts appeals action ignored rule made independent determination discriminatory purpose disagree view followed legal principles rejecting district finding discriminatory purpose concluding finding purpose compelled relevant evidence majority concedes must appeals acknowledged correctly stated controlling standard rule ante opinion appeals plainly findings fact may overturned either clearly erroneous made erroneous view controlling legal principles furthermore majority notes ante appeals justified decision reject district finding seniority system result purposeful discrimination stating analysis totality facts circumstances surrounding creation continuance departmental system leaves us definite firm conviction mistake made emphasis added omitted frankly loss understand appeals expressed conclusion district finding issue intent clearly erroneous precision clarity majority rejects appeals clear articulation implementation rule apparent ground course correctly setting forth requirements rule also included following quotation prior decision east romine although discrimination vel non essentially question fact time ultimate issue resolution case expressly proscribed finding discrimination nondiscrimination finding ultimate fact cites omitted reviewing district findings therefore proceed make independent determination appellant allegations discrimination though bound findings subsidiary fact clearly erroneous neither arguments justifies majority conclusion cases must remanded fourth trial merits aware rule decision embraced places dispositive weight whether accurate statement controlling principle appears early late opinion majority suggest basis unique rule interpretation long acknowledges proper legal standard think irrelevant whether chooses set forth standard beginning end opinion heart majority argument therefore failure remand action district rejecting conclusion seniority system bona fide within meaning indicates appeals properly follow rule addressing issue however necessary examine nature finding intent required teamsters procedure courts appeals follow reviewing district finding intent extent adhered procedure case district examined four factors approved fifth circuit james stockham valves fittings cert denied determine whether departmental seniority system adopted maintained discriminatory purpose although indicating four factors way demonstrate existence discriminatory intent today implicitly acknowledges proof factors satisfies requirements teamsters particular majority agrees finding discriminatory intent sufficient satisfy teamsters based circumstantial evidence including evidence discriminatory impact see ante see also arlington heights metropolitan housing dev given nature factual inquiry appeals must first determine whether district applied correct legal principles therefore considered legally relevant evidence presented parties majority acknowledges legal function appeals must perform first instance ante second appeals must determine whether district finding respect intent supported legally relevant evidence holds today generally factual determination limited dictates rule finally appeals sets aside district finding respect intent either finding clearly erroneous based erroneous legal standard may determine interest judicial economy whether legally relevant evidence presented district permits one resolution factual issue ante one conclusion possible reviewing free find existence fact question matter law see bigelow virginia levin mississippi river fuel reading opinion demonstrates appeals followed precisely course examining issue discriminatory intent even majority concedes appeals determined district committed legal error failing consider relevant evidence resolving first third james factors ante respect first james factor whether system inhibits employees equally transferring seniority units district found departmental system locked negro white workers departments discouraging transfers district acknowledged negroes might suffer greater impact company previous discriminatory policy openly maintaining negro jobs white jobs caused negroes concentrated less desirable positions district concluded however differential impact irrelevant determining whether seniority system operated neutrally appeals properly held district erred failing consider fact departmental system locked negroes less desirable jobs similarly third james factor whether seniority system genesis racial discrimination district rejected respondents argument motives iam relevant concluded usw charged racial bias iam appeals held conclusion erroneous motives intent significant consideration whether seniority system genesis racial discrimination majority acknowledges findings fact made erroneous view controlling legal principles clearly erroneous rule apply findings may stand ante quoting see also kelley southern pacific general motors singer manufacturing parke davis rowe general motors found district findings first third james factors made erroneous view controlling legal principles appeals compelled set aside findings free requirements rule two findings set aside district conclusion departmental system bona fide within meaning also rejected since conclusion based least part erroneous determinations concerning first third james factors least therefore appeals entitled remand action district purpose reexamining bona fides seniority system proper legal standards however often noted cases remand inappropriate facts record susceptible one reasonable interpretation see dayton board education brinkman bigelow virginia supra cases ffective judicial administration requires appeals draw inescapable factual conclusion rather remand case district needless proceedings levin mississippi river fuel action particularly appropriate appeals good position evaluate record evidence district major premise behind deference trial courts expressed rule findings fact depend peculiarly upon credit given witnesses see hear yellow cab see also oregon state medical society indeed rule expressly acknowledges importance factor stating due regard shall given opportunity trial judge credibility witnesses consequently especially reluctant resolve factual issues depend credibility witnesses see generally oregon state medical society supra cases today usual deference required district findings fact entirely based documentary evidence noted general motors supra trial customary opportunity evaluate demeanor thus credibility witnesses rationale behind rule plays restricted role paper case see also jennings general medical findings trial based documentary rather oral evidence carry weight appellate review orvis higgins believe appeals correctly determined finding discriminatory intent compelled documentary record presented district respect three four james factors appeals found overwhelming evidence discriminatory intent first ruling district erred acknowledging legal significance fact seniority system locked negroes least remunerative jobs company appeals determined disproportionate impact demonstrated system operat discourage employees equally transferring seniority units quoting james stockham valves fittings second noting credible explanation ha advanced sufficiently justify existence two separate die tool departments two separate maintenance departments condition found plant creation departments time unionization subsequent years appeals concluded second james factor satisfied finally respect third james factor appeals found role iam properly recognized crystal clear considerations race permeated negotiation adoption seniority system subsequent negotiations thereafter reviewing relevant record evidence presented district appeals concluded doubt based upon record case existence discriminatory purpose fail see appeals erred carrying appellate function respectfully dissent majority decision prolong respondents quest vindication rights requiring yet another trial majority acknowledges ante stated gypsum finding fact clearly erroneous reviewing entire evidence left definite firm conviction mistake committed emphasis added contrary majority suggestion ante find nothing fifth circuit decision james stockham valves fittings imply factors constitute relevant criteria determining discriminatory intent conclusion seem compelled since majority notes james factors nothing summary criteria examined teamsters majority indicates ante discriminatory motive iam relevant extent may shed light purpose usw company creating maintaining separate seniority system issue case read appeals opinion action holding anything usw participated establishing system designed purpose perpetuating past discrimination third james factor satisfied given iam party litigation participation creation seniority system hardly deemed irrelevant therefore irrelevant appeals specifically hold district factual findings clearly erroneous two witnesses testified brief hearing district conducted question whether seniority system immune witnesses longtime negro employees testified behalf respondents concerning racial segregation plant usw indication district opinion relied upon testimony two witnesses concluding system bona fide within meaning remainder record district consisted entirely exhibits submitted respondents company unions concerning development maintenance seniority system say rule apply document cases see singer manufacturing however decision rests upon incorrect reading undisputed document appellate free substitute reading document eutectic metco see also mckensie sea land service best medium pub national insider cert denied ex rel binion cert denied although majority correct stating appeals refer expressly apply standard reaching conclusion ante emphasis added appellate adherence requirements rule nevertheless apparent following statement record evidence indicates significant number departments established upon unionization next twenty five years departments carved previously mixed departments establishment maintenance segregated departments appear based considerations objective separate races emphasis added whether appeals expressly ruled fourth james factor irrelevant appeals clearly stated conclusion based totality facts circumstances surrounding creation continuance departmental system see also crystal clear considerations race permeated negotiation adoption seniority system subsequent negotiations thereafter consider significant decision conditions racial discrimination affected negotiation renegotiation system even assuming district correct concluding system maintained free illegal purpose appeals entitled conclude discriminatory intent demonstrated basis relevant evidence