FIFTY YEARS later, the landscape of American race relations looks so radically different that it is hard to remember what the nation looked like before the Supreme Court's decision in Brown vs. Board of Education.

But in 2004, an increasing number of people are openly asking whether Brown failed, because public schools remain so highly segregated 50 years later.

This is a dangerous argument. The Brown case was never only about schools. It was the leading edge of a fight against racial segregation in all of American life.

In 1989 and 1990, I had more than six months of interviews with Supreme Court Justice Thurgood Marshall. The child of Baltimore's segregated school system, Justice Marshall was not afraid to argue the value of Brown in terms of ending the damage done by supposedly separate but equal schools. He knew the schools for black children had the hand-me-down books, the overcrowded buildings and teachers, including his mother, who were paid less than any white teacher.

But Mr. Marshall also knew that the legacy of the Brown decision that outlawed racially separate public schools was being questioned. In fact, the man who later succeeded Justice Marshall on the high court made the most compelling argument against Brown.

Writing in 1987 when he was chairman of the Equal Employment Opportunity Commission, Clarence Thomas argued that the NAACP Legal Defense Fund should have made the case for quality schools for all Americans, regardless of race, when it argued the Brown case. It should not matter, he said, if a black child sits next to a white child. The key, he said, is that every child gets a quality education that allows him or her to succeed in a competitive society.

Americans should be released from "petty squabbles over quotas, affirmative action and race-conscious remedies for social ills." Mr. Thomas proposed that Americans focus on improving schools for all children without regard to their race - along the lines of liberty, brotherhood and equality, as described in the Declaration of Independence.

Mr. Thomas made a good argument.

When I mentioned it to Justice Marshall, he made the case that he had never been interested in creating classrooms with a rainbow of skin colors. The heart of Brown, he contended, was that it ensured equal access to all public schools for all children. He assumed that the white majority wanted to give its children the best schools. And having seen the inferior schools provided by white school boards to black children, he wanted to make sure that those education officials had motivation to provide black children with good schools. The motivation was simple: The black children had the right to go to the schools for white children.

Justice Marshall's theory remains valid to this day. But in the 50 years since Brown, it is also true that the theory has been distorted. First it was assaulted by "massive resistance" from segregationists who vowed never to allow school integration. That is the "squabbling" over racial issues that Mr. Thomas mentioned in his argument.

The Supreme Court did not help when it allowed school districts to delay integration and proceed with "all deliberate speed." That prompted stalling tactics and led to conflict and fear around implementation of school integration.

Most areas of the nation did not begin to see school integration until the late 1960s. And in 1974, 20 years after Brown, the Supreme Court ruled that suburban school districts had no obligation to mix students with urban school districts to achieve school integration. That gave families with enough money to move to the suburbs an easy way out of dealing with the controversy over school integration caused by segregationists.

Today, America's public schools are more segregated than they were in 1970. The top 27 metropolitan areas in the country, including Baltimore, have public school populations that are overwhelmingly nonwhite. And racial segregation is only part of the story. The schools with heavy black and Hispanic populations also serve a disproportionately poor population. And by most measures, they offer an inferior education: high dropout rates, fewer experienced teachers and fewer students who score well on standardized tests and advance to top colleges.

But the problems of school integration are not the heart and soul of the legacy of Justice Marshall's work in Brown. They never have been.

It may be hard to believe, but before Brown, the federal government enforced the laws of segregation in all American life based on the 1896 Plessy vs. Ferguson decision that certified separate but equal as the law of the land in all areas of American life. In one dramatic ruling - Brown - the power of the federal government literally changed sides on racial integration.

The courts, the White House, the Justice Department and the FBI shifted from quietly standing by the laws of racial segregation to the diametrically opposite stand of sending troops to Little Rock, Ark., in 1957 to defend the rights of nine black children who wanted to attend Central High School.

The media also changed gears and began to focus on the civil rights struggles of blacks. The year after Brown, the Montgomery, Ala., bus boycott took place. Major newspapers that had ignored previous boycotts against segregated buses now paid attention. The result was that the Rev. Martin Luther King Jr. became known nationally as a charismatic leader of a growing national civil rights movement. More boycotts, Freedom Rides and voting rights marches followed.

By 1964, the fire started by the Brown decision had created such political heat that Congress finally was roused to pass the Civil Rights Act and then, in 1965, the Voting Rights Act.

Another byproduct of the Brown case is the increasing number of minority high school and college graduates in the past 50 years. That has led to the largest black and Hispanic middle class in American history, along with more black political power on school boards, in city halls and in Congress.

Brown is the linchpin to American race relations, as we know it at the start of the new century. It is the ideological center of America's highest aspirations - our claim to be a just society. It is the basis for the promise of equal opportunities that draws a record number of immigrants to America. The legal strategy used in the Brown case remains the basis for arguments over equal rights under the Constitution for women, for gays, for children as well as for supporters and opponents of abortion rights.

Brown also set in motion arguments over affirmative action in hiring as well as admission to college and universities.

This is a stunning record of social and political transformation. It is a social and political revolution that has embellished American democracy and raised the nation's promise of justice for all to new heights.

Fifty years after Brown, Justice Marshall has no need to worry about the legacy of Brown. The evidence of magnitude of that stunning victory keeps growing.

Juan Williams, a senior correspondent for National Public Radio, is the author of Thurgood Marshall: American Revolutionary (Times Books, 1998).