Washington ? The Supreme Court’s upcoming ruling on affirmative action in college admissions has the potential to subtly or significantly affect the nation’s 15,000 school districts, many of which have long considered race in shaping student enrollment plans.

Already, lower court rulings in recent years have directed some districts — and led many others — to abandon race-based plans. The Supreme Court’s higher education ruling could invite schools to revisit that use of race or to eliminate it as a factor.

“Everybody sees the handwriting on the wall,” said Michael Simpson, assistant general counsel for the National Education Assn. “If the court says diversity is not a sufficiently compelling state interest to justify race-based admissions, there is every reason to expect that principle would apply to student assignment at the K-12 level.”

The Supreme Court heard arguments last week on two University of Michigan cases that challenge whether admissions policies favoring minorities are constitutional. Dozens of K-12 groups expressed their opinions in court papers, from teacher unions and black educators to school principals and state education boards.

Most took the university’s side, arguing that diversity provides essential benefits and that schools should have authority to ensure it exists in the classroom. For elementary and secondary schools, the implications of the court decision, expected by July, will depend not just on its substance but also on how broadly is it worded.

“The worst-case scenario would be a sweeping opinion that would resegregate higher education,” said Julie Underwood, general counsel for the National School Boards Assn. “The worse worst-case scenario would not allow any kind of race consideration in K-12. We would see a resegregated society very quickly.”

An increasing number of federal courts has lifted mandatory school desegregation plans and ruled in favor of those who believe K-12 race preferences are wrong.

In Maryland’s Montgomery County, just outside Washington, a court struck down a diversity policy that kept a white student from transferring from his minority-dominated school to a largely white school. Allowing him to transfer, school officials contended, would only fuel the increasing “racial isolation” of a school that had mostly black and Hispanic students.

In San Francisco, school officials changed course to settle a lawsuit by Chinese-American students who were not admitted to their preferred schools. The district repealed 45 percent caps for racial or ethnic groups at each school and 40 percent caps at magnet schools.