The new majority of the Montgomery County School Board, which has pledged to try to remove School Superintendent Charles M. Bernardo, voted last night to ask a court to invalidate his contract.

The board's vote was 4 to 2, with the majority formed by the three board members elected last month plus the one incumbent sympathetic to them.

Their position is the opposite from that of the old board, which decided to reappoint Bernardo -- extending his contract for four years -- last June, 3 1/2 months before the date the board was required to notify him whether or not he could keep his job.

Specifically, the new board decided to change its position on a suit filed against the board in Circuit Court in September by Henry B. Heller, president of the Montgomery County Education Association (MCEA), bargaining agent for teachers. Bernardo is also a defendant in the suit, which could be heard as early as Dec. 20.

That suit seeks to invalidate Bernardo's contract on grounds that the board violated a state law by reappointing him so far in advance. Last night's vote changed the board's position to agree with the MCEA's contention that the contract is invalid.

Following last night's board meeting, Bernardo continued to insist his contract is valid. "I have reaffirmed my resolve to completely fulfill my obligations" as superintendent, he said. He declined further comment on the board's action, as did board members.

Members of the previous school board who voted to extend Bernardo's contract in June said they wanted to see the reappointment issue out of the way early so it would not become a campaign issue in the fall elections.

But Bernardo, whose policies have become controversial among some parents and teachers, did become a campaign issue.

Three of the board's seven seats were up for election and the winners had criticized Bernardo because of 23 school closings that have occurred during his three years in office, his creation of a mandatory black studies course for school employes and his establishment of an innovative but untested computerized instruction system.

The new majority consists of new members Joseph Barse, Carol Wallace and Eleanor Zappone plus incumbent Marian Greenblatt. They were opposed in last night's vote on the court action involving Bernardo's contract by incumbents Daryl Shaw and Elizabeth Spencer. Board member Blair Ewing was not present for the vote, but his colleagues noted for the record that he had opposed the motion during a five-hour executive (closed) board session that preceded the public vote. David Naimon, the student member of the board, abstained from voting.

Greenblatt was elected the new board president, and Barse vice president on 4-to-3 votes, with Ewing, Shaw and Spencer voting against them.

Only last week, Bernardo's critics on the board conceded they would have difficulty finding a way to legally remove Bernardo. The state school superintendent alone has the authority to approve or remove a local superintendent, and state law says this can be done on grounds of immorality, misconduct, incompetence or willing neglect of duty.

MCEA leader Heller remarked on the board's action last night: "They're not playing parliamentary games, they're not hemming and hawing... They're looking for a legal means of replacing" Bernardo.