IT'S UNFORTUNATE that the Prince George's County desegregation suit remains fastened on school-by-school racial balances. Perhaps the history of this case, reaching back over the past decade, makes it inevitable. But maintaining specified enrollment ratios through the extraordinary demographic changes of the 1970s was probably not possible--let alone desirable. That seems to be the thrust of the past two weeks' testimony before federal Judge Frank J. Kaufman in Baltimore; there is perhaps another two weeks of it ahead.

In the fall of 1971, enrollment in the Prince George's County schools was 163,000 children. By last fall, it had dropped to 116,000 children. The movement of black families into the county, largely from the District of Columbia, was more than offset by the movement of white families out, and by the effects of dropping birth rates. Over those 10 years, the black enrollment rose from 22 percent of the total to 52 percent. In a smaller school district, it would not be unreasonable to expect administrators to accommodate even this kind of swing without large racial disparities between one school and another. But in a system as large as Prince George's County's, it would have required busing on an inordinate scale, with continual basic revisions of the attendance zones to reflect change in residential patterns.

As plaintiff in the case, the Prince George's branch of the NAACP has several reasons for its reliance on enrollment statistics. Its basic argument is that the county never fully complied with Judge Kaufman's original desegregation order in 1972. Beyond that, the statistics avoid the necessity for difficult and subjective judgments about quality in education. But the real issues now are exactly that --quality, and equality, of education in the county's classrooms, to which the enrollment data no longer provide a useful guide.

Remedies will not lie in the endless manipulation of enrollments, but in workable compromises among the different kinds of education that different children need--children not only of different races but of different kinds of family background, different levels of ability and different ideas about their own futures. If this litigation leads back to an emphasis on race and racial ratios as the overriding priority in student assignments, it will have done a disservice to the county's children. But if it can reinforce the schools' attention to the great diversity among its children, this suit may well make a useful contribution to the education not only of black children but of all the children in the county's classrooms.