Early in 1952, a psychologist on the staff of the American Jewish Congress by the name of Isidor Chein took the witness stand in federal district court in Virginia. He was testifying on behalf of the NAACP, America's leading civil rights organization, in one of the several school segregation cases that would ultimately be bundled together and named for a piece of litigation from Topeka, Kansas: Brown v. Board of Education. When it came time for cross-examination, the defense lawyer did not initially ask about the evidence, Chein's study on the "detrimental psychological effects" of segregation. He asked instead about the witness's name. "What kind of name is that?" he inquired of Chein. "What sort of racial background does it indicate?" After Chein said that his was a Jewish name, the attorney followed up by asking, "Are you 100 percent Jewish?" He did not drop the line of questioning until he had elicited from Chein the fact that his parents were not "native born in the United States." They had been born, Chein admitted, in Poland. All this lawyerly effort at casting doubt on Chein's bona fides as a white, even as an American, was no accident. In the years leading up to the Brown ruling in 1954, which is also to say the decade after the revelation of the Holocaust, American Jews felt acutely their vulnerability to race hate, their shared self-interest with Negroes (as the favored term was at the time) and ethnic Catholics in the battle against bigotry. "The fate of the Jews," Chein had put it once, "is bound up with the fate of all minority groups." Indeed, as Richard Kluger illustrates in Simple Justice, his magisterial history of Brown v. Board of Education, a Jewish thread ran through the legal assault against segregation. One of the first Jews on the Supreme Court, Felix Frankfurter, served as a mentor to the pioneering black civil rights attorney Charles Houston. Thurgood Marshall's right hand at the NAACP Legal Defense Fund was Jack Greenberg, who had risen from Brooklyn through a segregated Naval unit in World War II to Columbia Law School. In Topeka itself, a geographically Northern city with a Southern mode of racial division, the liberal, interracial circles included Jews drawn there by the Menninger Foundation's center for mental-health research. Some of those Jews were Eastern European refugees from Nazism. Some marched together with Negro war veterans as members of the left-wing American Veterans Committee. Jews and blacks were barred from the same elite country clubs. And so while Jack Greenberg cast the Jewish role in Brown as one of universal values - "It was a matter of human liberty," he said at one point - there is no shame in acknowledging just how much a practical recognition of common goals created the transracial alliance. Both idealistic and pragmatic, the mid-century partnership, which extended a decade past Brown into the civil rights movement, remains rightfully a source of Jewish pride, as well as no small measure of self-congratulation and nostalgia. IT HAS ENDED - at least the legal principle of it has ended - not with the proverbial bang but with a whimper. Late last month, the Supreme Court by a 5-4 vote ruled that it was unconstitutional for public schools to employ even voluntary integration programs based on racial composition. Much of the news coverage and immediate reaction to the ruling treated it as a devastating blow to the cause of desegregation, which has been treated in America as a proxy for equality. Yet Juan Williams, the biographer of Thurgood Marshall, struck much closer to the truth when he wrote in The New York Times that most urban school systems are now overwhelmingly black and Hispanic, making meaningful integration a statistical impossibility. Moreover, many African-Americans have stopped believing that desegregation in and of itself provides the answer to improving public education, at least in elementary and secondary school. The more consequential and volatile battles about equality these days turn on the ability of colleges to weigh race as a factor in admissions. THE JEWISH part in this transformation has been both ideological and geographical. For all their espoused tolerance, Jews were even quicker than other whites to move out of neighborhoods and schools that had reached some kind of racial tipping point in the 1950s and 1960s. As apartment-renters rather than home-owners, they could leave nimbly without losing equity. As believers in the elevating power of education, they were willing to pay the high property taxes to live in suburbs with top schools. The Jews who have reversed course by moving back into shaky urban neighborhoods are mostly Orthodox and Hassidic families that will not be relying on the lousy public schools. Even in suburbs, an increasing number of Jewish families, many not Orthodox, are sending their children to day schools and by definition detaching from public education. Still, these migration patterns explain only so much. You could date the Jewish estrangement from the civil rights coalition to the moment in 1965 when Stokely Carmichael declared "Black Power." Or you could date it to the New York City Public School strikes of 1968, which pit black community leaders (some flourishing anti-Semitic rhetoric) against a disproportionately Jewish teaching corps. Or you could date it to the DeFunis and Bakke court cases in the 1970s on affirmative action. By now, even the emotions of betrayal and recrimination - such fresh wounds in the late '60s and early '70s - have lost their sting. Diversity is the buzz-word of the land. On the 50th anniversary of the Brown decision, the most notable trend in American public education was the relentless resegregation of schools. And the one part of Isidor Chein's testimony that sounds most anachronistic now is his assertion that, because of the prejudice directed against them, American Jews feel inferior. For better and for worse, we have joined the white race.