The Montgomery County school board came under sharp attack yesterday as parents, educators, and civic group leaders convened a public forum to assess the potential for lawsuits against the board in the aftermath of last month's school-closing decisions.

Some 250 persons, including elected officials, state legislators, school principals, civil rights experts and scores of parents, attended the meeting where they denounced the board for taking actions they said will increase segregation in housing patterns and education. They used the forum at the United Presbyterian Church in Silver Spring to rally opposition to members of the board's conservative majority. Three of the conservatives are up for reelection next year.

The message yesterday, repeated frequently last month when the board voted on closings and boundary changes, was that the Takoma Park and Silver Spring areas will become isolated pockets of segregation, and that the result will be a deterioration of development, housing patterns and education in the area.

"We know where the minority population is, and we know what the school board is doing," said Norman Christeller, chairman of the county planning board and a former County Council member. "The school board is resegregating schools and this will have an impact on demographic patterns."

Lawyers who convened in a special panel at the forum said the board had taken actions that appear to "contain" minorities in specific sections of the county, such as the Montgomery Blair High School area of Silver Spring.

According to David Tatel, formerly head of the federalOffice of Civil Rights, such actions by a school board have been grounds for lawsuits elsewhere in the country.

Some lawyers at the forum said they believe that the board's decision last summer to raise the acceptable percentage of minority students in schools could be used as additional evidence of the board's effort to contain or isolate minority groups in the schools.

A number of communities are considering joining forces to challenge the board, both in appealing to the State Board of Education and in filing suits in federal court.

The school board, meanwhile, has received two memos from its lawyer regarding its actions on school closings. But the lawyer and the board have refused to release or discuss details of the memoranda, despite objections from board members Blair Ewing and Elizabeth Spencer. The board prohibits members from divulging to the public any information discussed in executive session.

Diana Pearce, director of research at Catholic University's National Policy Review Research Center, who has been conducting a study of the racial implications of the school board's decisions, said the bulk of schools designated for closings are ones that are evenly integrated.

"The burden is falling disproportionately on minority students and on integrated neighborhoods," Pearce said. In making its decisions, she added, the board was "sending a strong message . . . that if you live in an integrated community you have less of a chance of keeping your neighborhood school."

According to Pearce, the board's actions will result in virtually no decrease in segregation in the county. One effect will be to increase the percentage of elementary students now in schools that have more than60 percent minority students. If the board had followed the superintendent's plan, however, the percentage would have decreased by more than half, Pearce said.

Board member Marian L. Greenblatt, who defends the board's actions and says that "race" is a "buzzword" for dissatisfied parents, contends that the overall number of schools with minority enrollments exceeding 60 percent will decrease from 10 to seven.

Minority students make up roughly 20 percent of the total student population. Greenblatt has presented figures showing that33 percent of the students affected by the closings are minority students, and that 16 percent of the high school students affected are black.

"This is hardly a pattern of adversely affecting black students," she said last week