For more than 50 years, liberal and conservative Supreme Court Justices have disagreed about the central meaning of Brown v. Board of Education, the landmark 1954 Supreme Court ruling that outlawed public school segregation. Was the purpose to achieve a colorblind society or an integrated one?

When the Supreme Court ruled in June that public schools in Louisville, Kentucky, and Seattle, Washington, could not consider race when assigning students to schools in order to achieve integration, the Court came down firmly on the side of colorblindness.

The lawyers who won the Supreme Court case predicted that it would have as dramatic an effect on American society as the original Brown case did. "These are the most important decisions on the use of race since Brown v. Board of Education," said Sharon Browne, the principal lawyer for the conservative Pacific Legal Foundation.

In a 5 to 4 decision, the Supreme Court declared that public school systems cannot seek to achieve or maintain racial integration through measures that take explicit account of a student's race. More specifically, the opinion invalidated programs in Seattle and Louisville, Ky., that tried to maintain school-by-school diversity by limited student transfers on the basis of race or using race as a "tiebreaker" for admission to particular schools.

Both programs had been upheld by lower federal courts and were similar to plans in place in hundreds of school districts around the country. Chief Justice John G. Roberts Jr. said such programs were "directed only to racial balance, pure and simple," a goal he said was forbidden by the Constitution's guarantee of equal protection.

"The way to stop discrimination on the basis of race is to stop discriminating on the basis of race," Roberts said. His side of the debate, the Chief Justice said, was "more faithful to the heritage of Brown," the landmark 1954 decision that declared school segregation unconstitutional.

In his dissent, Justice Stephen G. Breyer said the decision was a "radical" step away from settled law and would strip local communities of the tools they need, and have used for many years, to prevent resegregation of their public schools. Predicting that the ruling would "substitute for present calm a disruptive round of race-related litigation," he said, "This is a decision that the court and the nation will come to regret."

The Louisville and Seattle cases— Meredith v. Jefferson County Board of Education and Parents Involved in Community Schools v. Seattle School District No. 1—were brought by parents whose children were not allowed to go to the school of their choice because of plans that seek to keep racial balance within a particular range.

Efforts to integrate schools have been a hot button in education for more than a half-century. There was the fight over segregation that led to Brown v. Board of Education in 1954; the 1957 trauma over integrating Central High School in Little Rock, Arkansas; the widespread busing battles in Boston in the 1970s; and the long and intimate federal court oversight of desegregation in many of the nation's cities. (See "1957: The Integration of Central High" and timeline, pages 26-27 in the Sept. 3 issue of Upfront, and "10 Supreme Court Cases Every Teen Should Know," pages 8-11 in the Sept. 17 issue of Upfront.)

The Supreme Court ruling has reignited a societal debate about the role of race in education that will almost certainly prompt divisive lawsuits around the country. And many school districts across the country may be forced to revise or abandon race-based student assignment plans.

There are no reliable statistics on how many districts try to achieve racial balance by using race in decisions about which students go to which schools; estimates range from a few hundred to nearly 1,000. Some states specifically call for such plans.

Education lawyers agree that the decision will lead more districts to consider income as a race-neutral means of achieving school diversity, as is already done in Wake County, N.C.; La Crosse, Wis.; Cambridge, Mass.; and elsewhere.

In light of the court ruling, school officials are already emphasizing newer efforts to promote diversity with the indirect emphasis on race they believe the court will tolerate. They include placing appealing academic programs in schools that have particularly heavy minority populations in an effort to attract more white students and possibly redrawing enrollment boundaries around economically diverse neighborhoods to bring a broader mix of students to certain schools.

"School districts are going to continue to do indirectly what they tried to do directly," says Peter H. Schuck of Yale Law School. "They will feel the same pressures to reduce racial isolation, and they will look for proxies for race."

William Yardley and Tamar Lewin cover education for The New York Times. With additional reporting by Jeffrey Rosen for The Times.