Building new schools on neighborhood boundaries and devising more complex ways to assign students to schools are among the techniques to achieve racial balance that school officials will resort to after yesterday’s Supreme Court decision limiting the authority of cities to assign students according to race.

Other cities may simply drop what efforts they had made to engineer the racial composition of schools.

The 5–4 ruling striking down race-based assignment plans in schools in Louisville, Ky., and Seattle, Wash., is expected to prompt new challenges to race-based systems for assigning students to public schools in Los Angeles and in St. Louis, Mo. In New York City, which scholars say has some of the most segregated public schools in the nation — some have no white students at all — the decision may mean the end of court-ordered desegregation rules that govern admission to eight of the city’s public schools.

“What the government is not permitted to do,” the swing vote in the case, Justice Kennedy, wrote, “is to classify every student on the basis of race and to assign each of them to schools based on that classification.”

Justice Kennedy wrote that the ruling “should not prevent” school districts from finding other ways to bring a racial balance to classrooms. He suggested placing schools along the borders of racially distinct neighborhoods and assigning students to schools by using reviews that consider race as only one among other attributes.

Some professors say the ruling will unleash a rush of experimentation, as school districts find ways to integrate schools without running afoul of the court’s prohibition.

A law professor at the University of California, Berkeley, Goodwin Liu, said school officials in rapidly growing regions such as the Southwest will likely take note of Justice Kennedy’s point about siting new schools.

“This could be very relevant in high growth areas,” Mr. Liu said. “When there is an opportunity to build schools, school officials will not be violating the Constitution if they take race into account in deciding where to put the schools.”

Justice Kennedy was alone among the majority in suggesting that local school officials could make race a part of their decisions. Chief Justice Roberts and Justices Alito, Scalia, and Thomas all took a stricter position.

“The way to stop discrimination on the basis of race is to stop discriminating on the basis of race,” Chief Justice Roberts wrote in their decision.

As the swing vote on the matter, Justice Kennedy’s opinion is understood as controlling. He called Chief Justice Roberts’ stance “all-too-unyielding.”

Race, Justice Kennedy, found “may be taken into account” so long as it never emerges as the primary way in which schools identify and classify students.

But that standard is not further fleshed out.

In a portion of the opinion that is sure to be studied closely, Justice Kennedy suggested that he would accept “recruiting students and faculty in a targeted fashion.” Several law professors interpret that to suggest that public secondary and high schools could foster affirmative action programs like university practices, such as that of the University of Michigan Law School, that have survived Supreme Court review.

But what works at college may not work in grade school.

“It’s virtually impossible for large urban school districts to sit down and interview 10-year-olds who want to go to elementary school and distinguish them as individuals,” a visiting fellow at the American Enterprise Institute who worked on a brief in the case, Edward Blum, said.

In the face of such uncertainty, schools may simply stop pursuing integration, some professors say.

“Schools are not going to know what they are permitted to do,” an education professor at Brooklyn College, David Bloomfield, said. “I think they are going to be paralyzed while they search around for some different formula.”

“I think a lot of schools are going to give up,” a Columbia Law professor, Nathaniel Persily, said of how he expected schools to react to the opinion.

In New York City, school officials say they do not assign students to schools according to race. The exception is eight schools that have been under court de-segregation orders since the 1970s. But the city’s department of education is now investigating whether yesterday’s decision could convince a judge to lift the orders.

An 11-year-old of South Asian descent, Nikita Rau, was recently rejected by one of the eight schools, Coney Island’s Mark Twain School, even though her test scores were two points higher than the cutoff for white students. The decision could make it easier for her and students like her to get into the schools of their choice.

Some integration advocates in the city decried the decision.

“Our fear is that our ability to maintain or increase diversity at the city schools will be compromised,” Kim Sweet, the executive director of a city nonprofit, Advocates for Children, said.

New York City’s schools are already so segregated that a 2005 book by Jonathan Kozol likened the situation to that of South Africa under Apartheid.

The director of UCLA’s Civil Rights Project, Gary Orfield, said “New York City officials have consistently claimed nothing can be done and that they can equalize the segregated schools. It has never happened.”

The city’s schools chancellor, Joel Klein, in an appearance yesterday on WNYC radio, said, “Almost three quarters of our students are African American and Latino. In an environment like that, a focus on racial balance seems to me to be not the way to solve the problem. A focus on high-quality education for every kid in every school I think is the way.”

The federal high court’s decision yesterday overturns all the lower courts to have examined the cases, which in both cities were brought by children who were barred from their preferred school. The two school districts used race to different extents in placing students. In Seattle it was used as a tie-breaker if a school was oversubscribed. In Louisville, race played a role only if the ratio of black students to white students swung too far in one direction.

In a dissent, Justice Breyer wrote that the majority, in interpreting the 1954 Brown v Board of Education decision as forbidding race-conscious school assignments, misunderstood the heart of that landmark opinion.
The majority, Justice Breyer wrote, “undermines Brown’s promise of integrated primary and secondary education that local communities have sought to make a reality.”

Justices Ginsburg, Souter, and Stevens joined the dissent.

The ruling prompted outcry from Senators Clinton, Obama, and Edwards, Democrats running for president. Mrs. Clinton faulted the decision for taking away “the right of local communities” to run their schools.