Segregation in U.S. schools increased during the last decade, despite the nation's growing racial diversity, according to a Harvard University study.

The study, released Tuesday, found that 70 percent of black students and more than one-third of Hispanic students attended predominantly minority schools during the 1998-99 school year, the latest data available from the National Center of Education Statistics.

The study also found that white students were more segregated from other minorities. While the average black student or Latino student attended a school that was 53 to 55 percent black or Latino, the average white student attended a school more than 80 percent white.

"White children are growing up in a society that is going to become more than half minority, and they are almost totally isolated from those minorities," said Gary Orfield, a Harvard professor and co-director of The Civil Rights Project that conducted the study. "These suburban kids are vastly unprepared for the future."

One reason the researchers cited for resegregation was the U.S. Supreme Court's 1974 ban on desegregation across city-suburban boundaries, which they said left central city schools overwhelmingly poor and overwhelmingly segregated.

"Cleveland is a classic case of a place that had to go through a desegregation experience that was very difficult and often counterproductive because the city and suburbs were so separate," Orfield said.

Last year, the Cleveland schools were released from court control, ending a 27-year-old desegregation case that required schools to reflect the racial composition of the district. Today, half of the district's more than 120 schools are considered all black.

The Harvard study's data also shows that Latinos have become increasingly isolated. In 1968, 23.1 percent of Latino students attended schools with a minority enrollment over 90 percent; in 1998, that number was 36.6 percent.

The 1990s, a decade which brought Supreme Court decisions limiting desegregation remedies, also saw an increase in the number of black students attending schools in which more than half the enrollment was minority, from a low of 62.9 percent in 1980 to 70.2 in 1999.

The Harvard study also included several recommendations, including creating metropolitan magnet schools with programs to attract students of all races across district boundaries, drawing foundation support to continue local programs aimed at integration, and promoting teacher exchange programs between cities and suburbs.