WASHINGTON — The Supreme Court on Thursday rejected the Seattle school district's racial tiebreaker, along with a school-integration plan in Kentucky, but left the door open for the limited use of race to achieve diversity in schools. The decision in cases affecting how students are assigned to schools in Louisville, Ky., and Seattle could imperil similar plans in hundreds of districts nationwide, and it further restricted how public school systems may attain racial diversity. The court split, 5-4, with Chief Justice John Roberts announcing the court's judgment. The court's four liberal justices dissented. "The way to stop discrimination on the...