After months of preliminary sparring, the Montgomery County school board and angry citizen's groups today enter the final rounds of the fight over school closings.

The school board has promised a decision by Dec. 1 on superintendent Edward Andrews' plan to shut down 31 schools during the next five years, 21 of them next June. Already more than 70 groups have voiced strong objections to the controversial plan, and board members have scheduled a month of public hearings, beginning this morning at Wheaton High School, to confront their complaints face-to-face.

Not only must the school board decide which schools to close, but also how and where students will be reassigned. Boundaries will be redrawn, and racial balances changed. More students will ride buses, and the concept of the neighborhood school will become obsolete in some sections of the county.

While many county residents accept the rationale behind school closings, some distrust the school board's motives. In the few weeks since the superintendent's final plan was released in August, neighborhood groups have charged that the school board majority supports certain school closings on racial and political grounds instead of on objective criteria.

"They are trying to bootleg segregation on the heels of an economic problem," says Harriet Bernstein, a former school board member who admits that during her tenure the board attempted to "bootleg desegregation" in the same way.

One group of parents, from the Takoma Park Junior High School area, charge that the board has pushed for a plan that is most disruptive to children living south of the beltway, where low-income and minority students are concentrated.

"We say we have growing enrollment and a growing, vibrant population," said Carolyn Bassing of the Takoma PTA. "Why do they want to close our schools? The concensus here is that it's because this is not a wealthy area."

There are also allegations that the board majority is trying to segregate students by returning to an old system under which all elementary schools include children in kindergarten through sixth grade. Previous boards had changed that structure in order to increase racial integration.

Finally, there are complaints that the board forced the superintendent into a plan assembled in haste which, in some instances, veers from the board's guidelines for school closings.

Faith Stern, chairman of the Takoma Park Response Committee that is gathering data to fight the closing of the school, says the plan "would increase instability and continue disruption" and "would clearly violate" several board policies.

"Can the board of education explain to us what we have done to deserve such shabby treatment?" says a letter from the group to the board members.

The board has pushed for school closures as a cost-saving measure and in response to a decade of declining school enrollment, a trend that is expected to continue for the next 15 years. From a peak of 126,000 students enrolled in 1972, there are now 95,000 students in the county's 177 schools.

Although 32 schools have closed since 1976, board president Carol F. Wallace says the process began too late.

"If the previous school boards had done what they should have done we wouldn't be in this mess today," Wallace says. "We're taking a lot of flack for things other school boards didn't do."

Wallace and Andrews insist that the plan is fair and that it meets the board's goals of improving racial balance without imposing busing for the sole purpose of achieving racial integration.

The return to K-6 elementary schools is educationally sound, Wallace says, and does not upset racial balance in the schools that will be consolidated.

She acknowledges that the board members themselves still disagree about some of the closings and says the public testimony will help resolve those differences.