The eventual decision on whether they can take race into account could affect hundreds of school systems in all areas of the country. The court accepted challenges to plans in Louisville, Ky., where the schools were once racially segregated by law, and in Seattle, where segregation was never official but was widespread because of residential patterns.
Federal appeals courts upheld these plans, both of which offer students a choice of schools while taking race into account in deciding which transfer applications to accept. Variations of this approach are common, and have been under legal attack around the country.
The Supreme Court's decision to add the cases to the calendar for its next term, a step that by all appearances was controversial within the court and unexpected outside it, plunged the new Roberts court into one of the country's deepest constitutional debates.
The action came three years after the court upheld a racially conscious admissions plan at the University of Michigan Law School. Writing for the majority in that 5-to-4 decision, Grutter v. Bollinger, Justice Sandra Day O'Connor suggested that, at least in higher education, affirmative action might be necessary for another 25 years.
The new cases do not ask the court to revisit that decision, and the justices are unlikely to do so. But the implications are far-reaching nonetheless. The eventual decision, roughly a year from now, could not only set the court's path in this area but could also shape the climate in which government policies with respect to race will be debated.
One difference between the Michigan decision and the new cases is that while the University of Michigan sought to use affirmative action to achieve a measure of racial balance, the school districts are trying to maintain such a balance.
In December, with Justice O'Connor still on the court, the justices refused to hear a challenge to a racially conscious student assignment plan in the public schools of Lynn, Mass. That plan, which a federal appeals court had upheld, is basically indistinguishable from the plans at issue in the new cases: Parents Involved in Community Schools v. Seattle School District, No. 05-908, and Meredith v. Jefferson County Board of Education, No. 05-915.
What has changed is the Supreme Court itself, with the retirement in January of Justice O'Connor and her replacement by Justice Samuel A. Alito Jr. One lawyer involved in the challenges to the Seattle and Louisville plans, Sharon L. Browne of the Pacific Legal Foundation, a conservative public-interest law firm, expressed the view that this change made the difference.
"I think the writing's on the wall, or at least I hope it is," Ms. Browne said in an interview Monday.
The plans under review in the new cases differ in details that are unlikely to prove constitutionally significant. The Jefferson County, Ky., school board adopted the Louisville plan in 2001, shortly after the school system was declared desegregated and was released from 25 years of federal court supervision.
The "managed choice" plan applies to all schools, kindergarten through 12th grade. In a district that is one-third nonwhite, every school is required to seek a black student enrollment of at least 15 percent and no more than 50 percent.
The Louisville case was taken to the Supreme Court by Crystal D. Meredith, a white parent whose son, Joshua McDonald, did not receive a requested transfer to attend kindergarten in a school that was trying to maintain a sufficient number of black students.
The plan in Seattle, which has struggled for decades to deal with the effects on its school system of segregated housing patterns, applies only to the city's 10 high schools. The policy is one of "open choice," subject to various "tiebreakers," one of which is race. Other factors include geographic proximity and whether a student has a sibling at the desired school, both of which count in favor of an application.
Under the "integration tiebreaker," high schools that deviate by more than 15 percent from the systemwide balance, which is 60 percent nonwhite, must take account of an applicant's race in order not to deviate further.
A group of parents organized as a nonprofit corporation called Parents Involved in Community Schools to fight the plan, and filed the Supreme Court appeal after losing by a vote of 7 to 4 in the United States Court of Appeals for the Ninth Circuit.
Both appeals reached the court in January and evidently provoked a vigorous internal debate among the justices, who considered the Seattle case six times and the Louisville case seven times before issuing the one-line order accepting both. Prolonged review of this sort is unusual.
Briefs are now likely to pour into the court in advance of a November argument; the University of Michigan case drew more than 100 briefs. But one of the more influential analyses may prove to be a brief concurring opinion in the Seattle case by Judge Alex Kozinski, the Ninth Circuit judge whose views carry great weight among legal conservatives.
Describing the Seattle plan as one "that gives the American melting pot a healthy stir without benefiting or burdening any particular group," Judge Kozinski addressed the Supreme Court justices directly, on the assumption that they would soon be reviewing the decision.
"There is much to be said for returning primacy on matters of educational policy to local officials," he said.
These were among the other developments at the court.
Speedy Trial
The court ruled unanimously that a federal defendant's rights under the Speedy Trial Act of 1974 were violated when, while seeking more time to prepare his defense to counterfeiting charges, he signed a statement presented by the trial judge in which he waived any future right to a speedy trial.
With certain exceptions, the federal law requires criminal trials to begin within 70 days after a defendant is charged. The trial for this defendant, Jacob Zedner, did not begin for seven years. Mr. Zedner eventually tried to assert his rights under the law and sought dismissal of the indictment, but two lower federal courts in New York enforced his waiver. He was convicted by a jury and sentenced to five years in prison.
In an opinion by Justice Alito, the Supreme Court ordered the indictment dismissed. The statute does not permit such a waiver, Justice Alito said, noting that the public as a whole, and not only an individual defendant, has an interest in the speedy administration of justice.
The significance of this decision, Zedner v. United States, No. 05-5992, is likely to transcend the particular case. Justice Antonin Scalia refused to sign the paragraph of the opinion in which Justice Alito cited the legislative history of the Speedy Trial Act as further evidence for his interpretation of the statute.
"The use of legislative history is illegitimate and ill advised in the interpretation of any statute," Justice Scalia's concurring opinion declared in what has become a familiar theme from him.
The fact that Justice Alito's paragraph of legislative history remained in the majority opinion, and that Chief Justice John G. Roberts Jr. signed the opinion without comment, indicates that Justice Scalia remains isolated in his view.
Sentencing
The court agreed to decide whether to give retroactive application to a 2004 decision that sharply limited judges' discretion to impose sentences above the thresholds set by sentencing guidelines systems.
The question is whether that decision, Blakely v. Washington, established a "new rule," in which case it is not retroactive, or whether it was a straightforward application of an earlier sentencing ruling, Apprendi v. New Jersey. The deeper issue in the new case, Burton v. Waddington, No. 05-9222, is how to tell a "new rule" from one that is not, a question that comes up with some frequency in habeas corpus cases.