THE SUPREME COURT held nearly 20 years ago that formerly segregated school districts could be required to bus to overcome neighborhood housing patterns, but not forever. Sooner or later, the court said, a complying school board could expect to have fulfilled its constitutional obligation; at that point the schools would be restored to the tradition of local control. That sounded fine -- in our system the schools do belong in local hands -- but it was vague. The court answered only in the most general terms the difficult next questions of how anyone would know when a district had done enough and what the district would then be free to do next. A divided court mostly continued to duck these questions in an Oklahoma City case last week.

The formerly dual or segregated Oklahoma City system is one of several that have asked in recent years to be declared unitary and to be allowed to go their own way. Typically these are larger urban and suburban districts that, among other steps, have been busing and now want for one reason or another to stop, generally in the lower elementary grades only. If they do stop, some all-black and all-white neighborhood schools will result. It will be argued that this is a different kind of segregation -- not the result of the official discriminatory policies that were the cause and definition of the original problem. But so far as separation of the races in the classroom goes (though not in matters such as racially separate faculty and administrative staffs) the school systems will be back where they started.

Should the court tell them yes, they have discharged their constitutional obligation, or no, they have not and must keep on trying?

The appeals court in the Oklahoma City case said to keep trying on the grounds (from anti-trust law) that a decree should only be lifted where unforeseen "dramatic changes in conditions" were causing a school board "extreme and unexpectantly oppressive hardships." The majority of five justices rejected this as inapplicable and a test that most boards could never meet.

Justice Thurgood Marshall urged the court instead to decide that all-black schools continue to carry the stigma and to be vestiges of the official segregation that the original Brown decision in 1954 was meant to eradicate; therefore a board proposing to re-create all-black schools by ceasing to bus must show it has no feasible alternative, like continued busing. The majority would not adopt that exacting standard, either (though neither did it expressly reject it).

Instead the majority simply sent the case back to the district court to decide afresh, without benefit of a fresh definition, whether the Oklahoma City system was now "unitary" in that it had destroyed the vestiges of past official discrimination "to the extend practicable." It's true the process of school desegregation can't go on forever, but the hard questions have mostly been left for another day.