Thirty years after the Supreme Court's landmark school desegregation decision, public support for desegregation of public schools is declining and segregation in education is increasing, according to a report released yesterday by the Joint Center for Political Studies.

But the center said in the report that there was "compelling evidence that desegregation works if it is done well" since the 1954 Supreme Court decision.

The report said that in the 1970s, blacks and whites began to "associate school desegregation with 'forced busing,' 'crime in schools,' and 'judicial arrogance,' " when desegregation actually increased resources for schools and in most cases improved the quality of education.

"We do not face a choice between benefiting blacks or benefiting whites . . . ," said the report, entitled "Thirty Years After Brown," a reference to the high court's decision in Brown v. the Board of Education of Topeka, Kan. "We face instead a choice of benefiting both races or neither. The history of school desegregation suggests ways to benefit everyone, if only we have the policy skill and political will to learn from the past."

The report said desegregation can be a "catalyst for educational changes" that benefit all students, such as reevaluation of curriculum, new training programs for teachers and administrators, and increased funding and public support for schools.

It added that under successful desegregation, "black student achievement increases, sometimes at a faster rate than white student achievement and sometimes to the point that differences in the performance levels of the two races disappear. White student achievement does not decline from desegregation . . . . Schools become more accessible to parents; patronage systems for hiring teachers and staff are shaken up . . . ."

However, the report's author, Jennifer L. Hochschild, said the steps needed to implement a successful desegregation plan are now politically unpopular. She criticized the Reagan administration's efforts to undo several plans that are in place.

"If whites are suddenly given reason -- through a Justice Department challenge -- to believe that they can be released from a plan, their declining opposition will skyrocket," Hochschild wrote. "Thus the very districts in which desegregation is beginning to work are those in which white resistance is being encouraged. Intentionally or not, the Reagan administration's actions are making desegregation as difficult and unsuccessful as it can be."

She cited Charlotte, N.C., Boston, and St. Louis as cities where desegregation efforts are working.

Jay Robinson, superintendent of the Charlotte schools, said in a later interview, "Our test scores are now the highest in the history of the school system. White flight has long ago stopped."

"If it's a matter of racial tension going down, then yes, things have become successful in Boston," said Ian Forman, assistant to the superintendent of the Boston schools. But he added that in general the black and white middle class has abandoned the schools and that one-third of the high school students are illiterate, although reading scores did improve last spring.

Among the keys to making desegregation work, the report suggests, are ensuring that schools have black and white supervisors; that neither race represents less than 20 percent of the student body, and that extracurricular activities are accessible.

Hochschild wrote that "if we do not desegregate schools in the largest cities and their suburbs we will have no further desegregation." She said that almost half of northern black students are in all-minority schools.