The Supreme Court yesterday confronted the difficult question of when school systems that once discriminated on the basis of race may be freed from court control.

Hearing their first busing case in more than a decade, a number of justices seemed skeptical that the Oklahoma City school system should be required to continue busing because of the persisting residential segregation that has resulted in one-race schools.

The case, Board of Education of Oklahoma City Public Schools v. Dowell, stems from the school board's 1984 vote to end 13 years of court-ordered busing for children in grades one through four and return to neighborhood schools. The move resulted in 10 virtually all-black schools in Oklahoma City, attended by 40 percent of black children in those grades.

"The school board has no realistic control over where people live," said Solicitor General Kenneth W. Starr, arguing for the Bush administration, which entered the case on the side of the school board.

"Today in Oklahoma City, no child is compelled to attend school by virtue of race," said school board lawyer Ronald L. Day. "The important thing today is that parents of all races have a choice."

But Julius L. Chambers of the NAACP Legal Defense Fund told the court that in Oklahoma City, "We have a segregated community that the state helped create" when schools were segregated by law. The court, he said, "should not let the school district in Oklahoma City, or in any other city, reinstate the same assignment practices that caused segregation in the past."

Justice Sandra Day O'Connor asked Chambers whether the school system would still be subject to the busing order 100 years from now if residential segregation in Oklahoma City persists.

"The order should remain and must remain in force until all vestiges {of discrimination} have been eliminated," Chambers replied.

"So the answer is 'Yes,' " O'Connor said.

Justice Antonin Scalia said that would mean busing is not a "transitional" solution, as the court has said, but a "permanent remedy."

The most emotional moments of the hour-long argument came when Justice Thurgood Marshall, the only black justice and the lawyer who argued Brown v. Board of Education on behalf of black schoolchildren, took on Day and Starr.

"How is the school board injured by being required to continue to operate the schools in conformity to the United States Constitution?" Marshall asked Day. "They weren't harmed that much, but the young black children were" who were relegated to all-black schools.

Nearly 30 years after the case was filed, "the poor Afro-American kid is still in the same school," said Marshall. "Then it still is a segregated school and you don't think segregation is unconstitutional," he told Starr.

"With all respect, Justice Marshall, that is emphatically not our position," Starr responded. He said the schools were majority black not by virtue of "state action" assigning children on the basis of race but because of demographics.

The case, which could affect hundreds of school districts nationwide, poses two questions for the court: How to tell when a formerly segregated school system has eliminated the vestiges of discrimination and achieved "unitary," or desegregated, status; and whether such a school system is under any continuing obligations, short of refraining from intentional segregation, to maintain desegregation.

But a number of justices appeared dubious about the need to continue court supervision. "It is not against the law for blacks and whites to go to school together any more in Oklahoma City," Justice Byron R. White told Chambers. "You're saying that they're back to their same old tricks. That isn't so, is it?"

Justice Anthony M. Kennedy said that in contrast to the past, when schools were separated along racial lines, "You're operating in an environment in which any family, assuming economic ability, can move to any neighborhood . . . . That's different."