Shortly before midnight last Nov. 2, the Montgomery County Board of Education made a quiet but dramatic decision: It voted to change the attendance boundaries of Montgomery Blair High School in Silver Spring so that fewer white students would attend the school.

The decision, made on a motion by board member Marian L. Greenblatt, was a surprise to everyone but the four board members who voted for it. They had conferred privately the weekend before to arrange the vote.

Few actions demonstrated so clearly the board majority's overall response to the demographic revolution that has reshaped Montgomery County in the past 15 years.

Members who voted for the boundary change say their "pragmatic" policies--including recent approval of supplementary funds for Blair--have helped improve education for all students, including minorities. They cite higher test scores countywide as evidence of their success.

But their critics, including two dissenting school board members, disagree. They charge that the boundary vote was symbolic of a raft of board actions that have undermined the county's efforts to cope with the growing minority and foreign population in Silver Spring.

"What the board is saying is that we should go back to the '50s and '60s and that what was appropriate for the school at that point is appropriate now," says Tommy Broadwater, president of the Blair Parent-Teacher-Student Association.

Blair G. Ewing, a school board member who voted against the boundary change, says the board lacks a clear philosophy. "We have had no discussion whatsoever about how to make an urban high school succeed," he says.

The consequences of the board's boundary decision were far reaching: Blair, with the highest concentration of minority and foreign students of any of the county's 22 high schools, would lose 400 students in five years. Its enrollment, already close to 60 percent minority, the acceptable level under board guidelines, would become increasingly lopsided racially. The school this year was 58.6 percent minority; the sophomore class, depicting a trend, was 63 percent minority. The shrinking enrollment would mean fewer teachers and resources, and would jeopardize the array of courses Blair offers to meet the diverse needs of its student body. With fewer students, a planned multimillion-dollar renovation of the main classroom area, the "C" building, would be put in doubt.

Beyond practical considerations, however, many parents and community leaders in Silver Spring and Takoma Park felt the board vote affirmed negative impressions in the county that Blair is a "ghetto" school where white parents would be afraid to send their children.

Board members who voted for the boundary change admitted that they did so at the request of white parents living north of the Capital Beltway who, given the planned closure of nearby Northwood High, threatened to send their children to private schools instead of Blair.

"It was like blackmail of the board, and they should not have bought it," says Janet Feldman, whose daughter is a Blair 10th grader and whose son, a 1981 graduate, attends Oberlin College. "They appear not to understand at all what is going on here. It's frustrating, because it seems there is no way to explain it to them."

But Greenblatt and her allies (only one of whom, Eleanor D. Zappone, has been to Blair in recent years) have denied that the board's action contributed to a negative image of the school. "Absolutely not," Greenblatt said recently. "It was irrelevant."

Within days of the Nov. 2 vote, Blair's future was uncertain. Suddenly there was talk of closing the school altogether, even though Superintendent Edward Andrews had called it "an anchor in the Silver Spring community."

School board member Joseph Barse, a Greenblatt ally, suggested converting it into a junior high, and shipping Blair-area high school students to schools north of the beltway. The "definite motivation" for his plan, Barse explained recently, "was to reduce the student capacity and avoid an expenditure of $3 million" for the renovation.

Zappone, now the school board president, proposed making Blair a magnet school for the performing arts, a suggestion greeted harshly in a community that has pushed for additional academic resources.

Blair-area parents, angered by the board's boundary change and other school closing actions, mobilized to challenge the board. They joined other neighborhood groups and filed suits against the board. Two months ago, a hearing examiner for the state Board of Education agreed with the parents, and Thursday, the state board met in special session in Baltimore to consider their appeal.The Blair parents group also won the attention of a state advisory panel to the U.S. Commission on Civil Rights.

"The general gut feeling here was that the board did something immoral," says Janet Feldman, whose husband, Martin, is active in the Blair PTSA and helped organize the lawsuits. "The only way we could explain the board actions was that they wanted to contain and isolate this high-minority area so that these kids would not have to go to schools with their kids in their areas."

Faced with mounting pressure from Silver Spring citizens, the board postponed further decisions on Blair until after school board elections in November, even though it had asked the superintendent to investigate future options for the school and present a report last winter.

Recently, the political debate enveloping Blair High has led members of the board majority to try to change their tack. Greenblatt, who is seeking the Republican nomination for Congress, and her allies have begun to blame the school's negative image on the Blair community, the media and policies fostered by the former liberal board, rather than on any of their own actions.

"The community is going to have to want to change the image and stop downgrading it," Greenblatt said. "There is an image problem. But the community itself has to feel good about the school."

These board members also credit themselves with agreeing to ask the County Council to approve "a tremendous infusion" of supplementary funds--$330,000--for Blair next year to help the "average student" who has been shortchanged because of the school's necessary commitment of resources to foreign and remedial students. And they point out that because of their actions Blair will have a French immersion program for any student who wants to enroll.

"I just hope that people start to realize that we have gone to bat for Blair in a heck of a lot of ways," said board President Zappone. "I don't think any board has done so much for any one school. What I would like to see happen at Blair is that the money have such an effect that people realize the diverse needs are being met. You change the perception by facing up to the problems, as we did."

Asked if the board's November decision to change boundaries was "facing up to the problems," Zappone replied that "the climate was not right" at the time to do anything else. But she said she was "tremendously optimistic" that the $330,000 would "mean the difference in how people view Blair."

School system officials and Blair parents agree that the added funds will help. But they are skeptical that money alone will change an anti-Blair, anti-Silver Spring attitude that they say is reinforced by the board's actions and its general philosophy on racial-integration issues.

A number of parents and other community leaders say they fear the board is wedded to paper policies and money solutions, and remains insensitive to the fundamental problems of student diversity in an increasingly urban section of the county.

"An 11th-hour conversion of throwing money at the school hardly gives them brownie points for their kindly solicitude of Blair High School," said former board member Harriet Bernstein, an active member of EdPAC, a political action committee formed to oust the Greenblatt faction on the school board. "Their timing does leave room for suspicion."

Board member Ewing stresses that the board still must address the problem of too few students at Blair. "The school badly needs a larger number of students," he said. "But they the board majority want to close their eyes and ears to that."

According to Zappone, even with its diversity, the number of students at Blair is not a problem because "board policy" says that the "ideal" size for a county high school is betwen 1,200 and 1,600 students. Blair, she said, which will shrink to about 1,490 next year from its current 1,725, "will still be in the ballpark."

The added money next year, she said, will help solve the academic strains that have resulted because one-quarter of the student body, some 500 students, are foreigners whose native language is not English.

Skepticism about the board majority's motives stems from their previous actions. Last summer, for example, the faction led by Greenblatt voted to increase from 50 percent to 60 percent the acceptable percentage of minority students in a school--the level at which school officials must look into ways to even the racial balance. With that percentage raised, critics charged, the board was under less pressure to send white students to Blair when new boundaries were considered during the countywide school closings last year.

"It's all very coolly calculated," said one school system official who asked not to be identified. "They listen to whatever is proposed, but they are very clever. They do it in little steps, but they see it as a whole."

The board's treatment of Blair, particularly the actions taken before the recent approval of funds, has angered students and faculty members alike. (Some graduating seniors who were concerned that Greenblatt might hand out diplomas at last Monday's commencement--a task she had performed the past two years--threatened to stand and turn their backs to her during the ceremony. But board member Carol F. Wallace, who abstained on the boundary change vote, was the representative this year.)

During the two-year tenure of principal Joseph Villani, many teachers say, the school's self-esteem has improved dramatically. The faculty is about 20 percent minority, and many teachers say they are committed to teaching in a heterogeneous setting. They are angry that the school's ethnic mix contributes to a perception that it is inferior to the 21 other high schools in the county.

Former school board member Daryl W. Shaw, who was principal at Blair from 1946 until 1962, when he moved to Walt Whitman High, the county's top academic high school, compliments the present Blair administration for its strenuous efforts to meet the needs of the diverse community it serves.

"Blair's diversity is a plus," said Shaw. "It is the kind of world the students today are going to live in. We need a situation that will let young people learn about life, and learn about the real world."