A Montgomery County judge said yesterday it will be at least another week before he decides whether the county school board may fire School Superintendent Charles M. Bernardo.

The present board, dominated by a new conservative majority, pledged during the election campaign last fall to remove Bernardo and has taken him to court in an effort to fire him.

The superintendent contends that the firing would be illegal because the former board acted legally when it extended his $53,500-a-year contract for four years. The former board acted more than 15 months before Bernardo's contract was due to expire.

Circuit Court Judge Jehn F. McAuliffe said after hearing final arguments yesterday he will reach a decision "soon after" next Thursday.

The board's majority, Marian Greenblatt, Joseph Barse, Eleanor Zappone and Carol Wallace, have attacked Bernardo because of unpopular decision on school closings and a massive reorganization of the school bureaucracy, which they say demoralized teachers and staff.

During yesterday's hearing, board attorney Roger W. Titus said the former board's action thwarted the "will of the electorate" and circumvented a state law governing the timing of appointments and reappointments.

Titus said the former board circumvented state law, which places the time for the decision whether to appoint or reappoint a superintendent in February before a superintendent takes office in July.

Joseph D'Erasmo, Bernardo's attorney, asserted that the contract renewal was "legal, binding and approved by the state superintendent." He said the former board renewed the contract last June because of a contractual obligation to give Bernardo a statement of its intent a year before his term was due to expire.

He said Bernardo, relying on the contract, purchased a Rockville home and turned down several job offers from "Dallas, Cleveland, New York" and the federal government.