The Maryland Board of Education, in an unprecedented action, voted unanimously yesterday to overturn the Montgomery County school board's decisions affecting three Silver Spring area schools that have been at the heart of efforts to improve school integration in the county.

In voting for the first time to overrule a closing by a local board, the state board found the Montgomery board was "arbitrary and unreasonable" in ordering the closing of Rosemary Hills Elementary and changing attendance patterns at Montgomery Blair High and Eastern Intermediate schools. The state board said the actions of the Montgomery board last fall, which ignored proposals by Montgomery schools Superintendent Edward Andrews, also were inconsistent with the local board's own guidelines.

The state board's action was a victory for minority groups and liberal activists who have repeatedly challenged the county board on racial policies during the last three years. It also will have an impact on this year's school board election, which is shaping up as a referendum on the policies of the conservative majority.

The three rulings were among 12 Montgomery school closings and boundary changes acted on yesterday in Baltimore. The state board upheld all but one of the recommendations made on April 22 by its hearing examiner, Mitchell J. Cooper. It reversed Cooper only in an appeal involving two elementary schools in Bethesda, voting that Radnor, not Bradley, should be closed. In the other eight appeals, the state board and Cooper sustained the county board's decisions.

The Montgomery board's decision to close Rosemary Hills, a national symbol of how to integrate schools without a court order, and to change the boundaries for Blair High, which has more minority students than any high school in the county, initiated a storm of protest from community groups and organizations, including the American Civil Liberties Union.

State board member Verna Fletcher, who was a member of the Montgomery school board when the Rosemary Hills integration experiment was approved seven years ago, said yesterday's findings contained "no punishments and no rewards."

The Montgomery board will now have to decide whether to change its decisions on Blair, Rosemary Hills and Eastern, or appeal yesterday's ruling to the county's Circuit Court. The seven-member county school board will meet this morning with its attorneys to decide a course of action.

"The state is saying that the Montgomery board has got to go back to the drawing board," said Gus Crenson, director of public information for the state board. Fletcher and state board president Joanne T. Goldsmith, a former vice president of the Prince George's County school board, said that they were careful not to suggest in any way what the Montgomery board should do.

Marian Greenblatt, a leader of the Montgomery board majority, said, "I'm appalled that the state board would interfere in the decisions of a local board. My own feeling is that we should take it to court. The state does not determine whether we open a school where or when and they shouldn't be interfering on our closing of a school. I don't think they should be in on this at all."

Board member Suzanne Peyser, who was elected on a slate with Greenblatt in 1980, concurred. "These were not cautious decisions at all," Peyser said. "I think in each case there was a judgment call. The local board had many outstanding reasons for the decisions we did and the state board failed to see this."

Greenblatt said she found the Rosemary Hills decisions "particularly ironic" because she said the state board's rulings would do less to improve racial integration in the Bethesda-Chevy Chase high school area than the plan the Montgomery board approved--a view disputed by board critics.

Board member Blair Ewing, one of two frequent dissenters on the school-closing issues, said the ruling represented "clear evidence of the local board's failure to follow its own policies. These decisions demonstrate as nothing else has done the utter incompetence of the Montgomery County school board," Ewing said.

The rulings are expected to have an impact on school board elections this fall and add fuel to the argument that the board has been insensitive to minorities.

"This proves that the board worked on a faulty sense of logic. People who felt that their communities had been given unfair decisions have been vindicated," an elated Vicki Rafel said yesterday. Rafel, a school board candidate, coordinated fund-raising for the consolidated Rosemary Hills, Blair and Eastern appeal to the state board. She predicted that the Montgomery board's credibility will suffer as a result of yesterday's rulings.

Roscoe Nix, president of the county's NAACP chapter and a former member of the county school board, said the state board's actions "should say to the community at large that this board has been authoritarian and dictatorial . . . interested in their own personal power rather than the education of children."

"These decisions have national implications," said Peter J. Nickles, an attorney who helped draft the appeals for Blair, Eastern and Rosemary Hills. "There is the phenomenon of declining enrollment everywhere, but this board is saying that we will not permit the gains in integration to be eroded with the device of school closings."

The nine-member state board, which includes two blacks and one Asian, was in unanimous agreement on all but two of the rulings yesterday. The board was unanimous on each of the three reversals of the Montgomery board, according to a voluminous report handed out yesterday.

In the Blair case, Superintendent Andrews had originally recommended a plan that would have added students from three predominantly white elementary schools located above the Capital Beltway in a move that would have reduced that school's minority population from 58.6 percent to 50 percent.

The school board rejected that plan, voting instead to withdraw some minority students from Blair without adding more majority students. E. Stephen Derby, a lawyer representing the school board, had argued that it was misleading to say Blair had too many minority students and that its student body of 34.7 percent black, 10.3 percent Asian and 12.5 percent Hispanic represented "a sound ethnic mix."

Rosemary Hills is one of 10 elementary schools that feed into Bethesda-Chevy Chase High School and has been part of an integration cluster with Chevy Chase and Larchmont elementaries in which students were assigned to Rosemary Hills for kindergarten through second-grade, then went to Chevy Chase, Parkwood and Larchmont for grades 3-6.

School board attorneys had argued that the Rosemary Hills closing would improve integration by dispersing its students among four other elementary schools. But the state board again found the current cluster arrangement "greatly alleviated" racial imbalance.

Sally Popper, who has a 5-year-old daughter at Rosemary Hills and co-chaired the ad hoc committee for Rosemary Hills that fought its closure, said, "After a difficult struggle of many months, this is a vindication."

In the case of Eastern Intermediate, the state board said that "in contrast to planning alternatives that would reduce the minority population in this school, the county board actions . . . have increased Eastern's minority enrollment (from 40 percent) to approximately 62.5 percent."

The state board again redeemed, without suggesting its use, a plan by Andrews that would have sent students from two majority schools to Eastern and projected the school's minority population at 44 percent. "Thus, there is at least one feasible alternative," the board said.

Despite the strident protestations of community members, the state board sustained the hearing examiner's recommendation upholding the county's decision to close Takoma Park Junior High, even though the board believed that "this is a school that 'works,' both as an educational program for the children. . . as well as a focal point for community activities."

The board yesterday also heard arguments, but made no decision, on an appeal by parents of former students at Leland Junior High School in Chevy Chase. Leland was closed last year. A hearing examiner has recommended that it be reopened.