Fifty years ago—on July 2, 1966—the federal government published “Equality of Educational Opportunity,”a landmark study by the Johns Hopkins University sociologist James Coleman that gave support for a novel idea about education: that schools should integrate based on the socioeconomic status of students.A dozen years earlier, the U.S. Supreme Court’s decision in Brown v. Board of Education had famously declared that schools segregated by race were inherently unequal and ushered in decades of efforts to desegregate schools by race. But the Coleman Report, which Education Week said is “widely regarded as the most important education study of the 20th century,” put a twist on Brown. It found that if one’s goal were to raise the academic achievement of pupils, then promoting a socioeconomic mix of students was even more important than changing the racial composition of the school.The impetus for the study was to get at the root of educational inequality by race. Authorized by Congress as part of the 1964 Civil Rights Act, the study was designed to examine inequality of opportunity in education “by reasons of race, color, religion or national origin.” Many expected the report to find the source of inequality in achievement between racial groups to be unequal spending between black and white schools, or racial school segregation itself.Instead, the report, which The New Yorker’s Nicholas Lemann called “probably the single best-known piece of quantitative social science in American history,” found that the biggest predictors of academic achievement were the socioeconomic status of the family a child comes from and the socioeconomic status of the classmates in the school she attends. Coleman wrote, “The educational resources provided by a child’s fellow students are more important for his achievement than are the resources provided by the school board.”A report conceived of as part of an effort to address racial inequality found that class inequality—and class segregation—mattered most. Racial school integration did generally benefit black students, the report found, but the “beneficial effect of a student body with a high proportion of white students comes not from racial composition per se but from the better educational background and higher educational aspirations that are, on average, found among whites.” Daniel Patrick Moynihan, the U.S. Senator who assembled a Harvard University study group to examine the Coleman Report’s findings, suggested, “we should begin to see that the underlying reality is not race but social class.” Dozens of subsequent studies, using more sophisticated techniques than those available to Coleman, have affirmed his results.For years after its publication, the Coleman Report’s key finding about socioeconomic integration was largely ignored by shapers of public policy, in part because it was seen as politically volatile. Liberals focused on equalizing school spending and racially desegregating schools, while conservatives advocated teacher accountability measures and private school vouchers. Once exception was Duluth, Minnesota, where, in 1972, policymakers floated the idea of integrating by schools by socioeconomic status. In an interview, Coleman endorsed the proposal, saying “a child’s performance, especially a working-class child’s performance, is greatly benefited by going to a school with children who come from educationally stronger backgrounds.” But the Duluth plan met political resistance and never got off the ground.Advocates of racial desegregation noted that while the Constitution requires the desegregation of schools that were once officially segregated by race, the Fourteenth Amendment doesn’t say anything about desegregation by economic status. This was unfortunate from an educational standpoint, Coleman noted, because racial desegregation did not always result in economic desegregation. For example, in Boston, Coleman noted, the racial-desegregation plan “involved primarily lower-class communities,” exempting “most of the higher-achieving middle-class schools in the suburbs” and was therefore unlikely to yield “beneficial effects on achievement.” By contrast, in places like Charlotte, North Carolina, racial school integration involved both working-class black students and middle-class white students, and achievement gains were considerable.In 1992, La Crosse, Wisconsin, became the first school district in the nation to put into effect an explicitly socioeconomic-based school-integration plan at the elementary-school level. One of Coleman’s Ph.D. students, Stephen Plank, studied the program and reported that while students initially grouped themselves by socioeconomic status, over time, children of different economic backgrounds mixed. Subsequent research showed that La Crosse saw achievement gains following adoption of the socioeconomic-integration program. Still, by 1996, three decades after Coleman’s report was published, just two school districts—La Crosse and McKinney, both in Texas—integrated schools by socioeconomic status. The two districts educated just 30,000 students.Over time, however, racial desegregation efforts began to wane as the Supreme Court instructed lower courts to wind down judicial supervision of school districts. For example, in the 1990s, Charlotte, which had been a great desegregation success story, ended its busing program and allowed the schools to re-segregate by race and class. Outcomes for African American students fell.Over time, the courts grew increasingly hostile to racially explicit integration programs. In 2007, the U.S. Supreme Court, struck down voluntary racial integration in Louisville, Kentucky, and Seattle. Seattle abandoned its integration plan, but Louisville chose to reinvent its program with an emphasis on parental income and education, consistent with Coleman’s original findings. In an ironic legal twist, the fact that Courts declined to recognize socioeconomic status as a “suspect class” like race in the 1970s now meant that rich people could not bring “reverse discrimination” suits to claim that they were being unfairly treated by plans that promote socioeconomic integration. Louisville’s program, which also considers the racial makeup of neighborhoods, is legally viable and has strong public support.Today, the number of school districts and charters pursuing socioeconomic integration has grown from two 20 years ago to 91, according to a Century Foundation study. These districts educate 4 million students. Charlotte, for example, which led the nation in racial desegregation, then abandoned it, saw its school board vote in 2016 to take steps to integrate the schools by socioeconomic status. (I am helping the district with its plan.)Many of the districts pursuing socioeconomic integration are seeing impressive results. In Cambridge, Massachusetts, for example, a socioeconomic-integration program was adopted in 2001 and by 2014, 86 percent of low-income students graduated, compared to 65 percent of low-income students in Boston, whose schools are not socioeconomically integrated. Coleman would not have been surprised by the 21-point differential. “Particular individuals who might never consider dropping out if they were in a different high school might decide to drop out if they attended a school where many boys and girls did so,” the Coleman Report explained. Moreover, socioeconomic integration often leads to racial integration, which has powerful benefits, such as reducing bigotry and forging social cohesion.For the past 30 years, the federal government has done little to encourage integration by socioeconomic status or race. Whereas the feds provided strong support for policies such as charter schools and merit pay for teachers, only modest efforts have been made to foster racial integration (through a $100 million magnet school program) and nothing for socioeconomic integration. Cautious federal politicians feared that supporting integration would produce a political backlash.In recent months, however, socioeconomic integration has begun to take the national stage. After years in which integration was seen as politically taboo, the new U.S. Education Secretary, John King, the country’s first African American and Puerto Rican U.S. Secretary of Education, is emphasizing school integration specifically by socioeconomic status—just as Coleman’s research suggested we should. King expanded the focus on magnet schools to include socioeconomic as well as racial integration. And the Education Department has proposed a new $120 million “Stronger Together” program to “encourage the development of innovative, ambitious plans to increase socioeconomic diversity through voluntary, community-supported strategies and expand existing efforts in states and communities.”James Coleman, who died in 1995, never saw the growth of socioeconomic-integration programs. But a half century after publication of his seminal report, school integration by social class is finally getting its proper due.