A half-century after the Supreme Court ordered the desegregation of American education, schools are almost as segregated as they were when Martin Luther King Jr. was assassinated, according to a new report released by Harvard University researchers.

The study by the Harvard Civil Rights Project shows that progress toward school desegregation peaked in the late 1980s as courts concluded that the goals of the landmark 1954 Supreme Court decision Brown v. Board of Education had largely been achieved. Over the past 15 years, the trend has been in the opposite direction, and most white students now have “little contact” with minority students in many areas of the country, according to the report.

“We are celebrating a victory over segregation at a time when schools across the nation are becoming increasingly segregated,” noted the report, which was issued on the eve of the holiday celebrating Martin Luther King Jr.’s birthday.

Triggered by a civil rights case in Topeka, Kan., the Brown decision marked the start of three decades of intensive efforts by the federal government to integrate public schools, first through court orders that opened white schools to minority students and later through busing. Its most dramatic effect was in southern states, where the percentage of blacks attending predominantly white schools increased from zero in 1954 to 43 percent in 1988.

By 2001, according to the Harvard data, the figure had fallen to 30 percent, or about the level in 1969, the year after King’s assassination.

“We are losing many of the gains of desegregation,” said Harvard professor Gary Orfield, the primary author of the report. “We are not back to where we were before Brown, but we are back to when King was assassinated.”

The Harvard study suggests that Hispanic students are even more segregated than black students, while Asian-Americans are the most integrated ethnic group in the country. The increase in Hispanic segregation has been particularly marked in western states, where more than 80 percent of Hispanics attend predominantly minority schools, compared with 42 percent in 1968.

Despite the national trend toward resegregation, there are significant differences among states and regions, Orfield said. Maryland is one of the most “rapidly resegregating states” in the country, he said, partly because of the phasing out of court-ordered busing in Prince George’s and Baltimore counties and partly because of migration patterns.

The District of Columbia has long been one of the most segregated school districts in the nation, a trend accentuated in recent years by the exodus of white middle-class families.

The most segregated states for black students are New York and Illinois; the most integrated are Kentucky and Washington. For Hispanics, the most segregated states are New York and California.