The Montgomery County Board of Education yesterday adopted a key policy change on racial balance that supporters say will help preserve neighborhood schools and critics charge will lead to the building of "educational Berlin walls" around schools with high minority enrollments.

The amendment to a policy statement adopted six years ago will curtail efforts to achieve racially integrated classrooms in county schools by redefining when imbalance exists. The 5-to-2 vote in favor of the amendment reflected the philosophical dominance of the board's conservative majority and was the most dramatic turn in a long day of emotional debate in a Rockvill hearing room crowded with TV cameras, PTA activists and minority group representatives.

Earlier in the day the board passed a resolution, deploring the rise in activity by hate groups in Montgomery County and calling for instruction in the nature of prejudice and propaganda in county English and social studies courses. Then the board abolished its minority relations monitoring committee with which it has had a less than amicable relationship, and later rebuffed calls for a public hearing on the racial balance policy change.

"This board is playing racial politics," charged member Blair Ewing, who voted against the policy change with Elizabeth Spencer, the last two liberals left on a school board whose direction and tenor has substantially changed over the last three years. "The board is playing on the fears and anxieties of the white community. What they're saying, in effect, is our interest is in assuring that minorities and the poor are kept in their place," Ewing said.

The policy change adopted yesterday alters the definition of when there are too many minority students in a particular school so that the school board does not have to act as frequently to try to remedy the racial imbalance. The result will be the preservation of the status quo in many of the 21 schools where there is an imbalance under the old definition. The greatest concentration of minority students is in the southeastern part of the county.

Marian Greenblatt, the school board chairman, called the change "sound policy" and said it was needed in order for the school system to adjust to "natural housing patterns" and the marked increase in the percentage of minority students in the county school system since the first racial policy was adopted.

However, critics fear the new policy will lead to the walling off of schools, a decline in the quality of education and increased racial polarization.

The board action comes at a time when many groups and public officials in Montgomery are trying to deal with an upsurge in the number of cross burnings and other racially related incidents in the county.

Wilma Fairley, director of human relations for the school system, said the policy change would lead to racial isolation and is bound up in the broader issue of race relations.

"The reason we are having so much difficulty with this issue is that we are fearful," Fairley said. "What we are seeing is that if you can't afford to live north of the beltway, you can't go to school there."

The board yesterday changed its Quality Education/Racial Balance policy, under which it committed itself in 1975 to seeking methods to adjust racial imbalances in schools where the minority enrollment exceeded 50 percent.

Under the revised policy, the board would consider ways to adjust imbalances only when minorities exceed by a percentage -- 38 percent -- the proportion of minorities in the whole school system. The current minority percentage in the school system is 22 percent, so under the new "floating figure," a school's minority population would have to exceed 60 percent before the board would take action.

As the minority percentage countywide in the school system continues to climb so would the percentage that would oblige the school system to look for ways to integrate the students.

Minorities and PTA members critical of the board's action yesterday also fear that the board will abandon the so-called school "cluster" system that was designed to encourage voluntary integration.

The board took no action yesterday that affects the future of the clusters in the county. But last month four board conservatives wrote a memo underscoring their support for the traditional pattern of organizing elementary schools from kindergarten through sixth grade, and future of the clusters is uncertain. "Clusters were intended to make minority populations more balanced," said Zoe Lefkowitz. "But clusters are definitely in jeopardy."