The Montgomery County board of education this week made its first cuts in the $265 million operating budget proposed by Schools Supt. Charles M. Bernardo, slicing out slightly more than 34 positions - 31 of them instructional - for a total savings of $425,720.

The largest single cut, proposed by board member Daryl Shaw and passed by a 4 to 3 margin, was the elimination of 16 high school teaching positions as a result of abolishing the seven-period day and returning to a six-period schedule in six county high schools.

This move was voted on at the end of a 2 1/2-hour budget session Monday night, after a motion by board member Blair Ewing to retain the seven-period day in all the 14 high schools that now have it failed by a 2-to-5 margin, with only Marian Greenblatt supporting Ewing.

Monday night's meeting was the board's second session on the budget this week, and the first at which any actual cuts were made. During the evening, the board combed through about 10 pages of the 550-page document, dealing chiefly with the instructional budget, which makes up 65 per cent of the budget total.

Most persistent about proposing staffing cuts, and most adamant that they be made, was board member Daryl Shaw, who repeatedly said that, while he disliked making staffing cuts, some cuts would have to be made in the budget to ensure that the County Council would fund the board-approved 6 per cent salary increase for county teachers.

Blair Ewing, board vice president Elizabeth Spencer and Verna Fletcher all voted against Shaw's proposal to eliminate the 16 high school positions.

Earlier in the evening, also on a motion by Shaw, the board voted 6 to 1 to raise the average elementary school class size in grades 1 through 6 to 26.9 pupils, thereby eliminating 13.2 elementary school teaching positions, for a savings of $156,000.

The present year's budget, as funded by the County Council, projected the same 26.9 figure as an average class size, but since enrollment projections were higher than this year's actual countywide enrollment of 48. All in grades 1 through 6, average class size in those grades this year stands at the figure of 26.5.

Bernardo's proposed budget had recommended an average class size of 26.7 pupils for the elementary grades.

The third cut proposed by Shaw and passed by the board was the elimination of three assistant principalships in the delementary schools, for a savings of $63,720.

Bernardo had recommended that, since the board closed five elementary schools this year, effectively eliminating five principal's jobs, that five new assistant principalships be created. Shaw's proposal cut this number down to two.

The cuts made by the board Monday night bring down the total number of fulltime school positions recommended in the budget from Bernardo's proposed 12,018 to less than 11,984. Thanks to the cuts, then instructional staff in the schools would go from the present 7,204 positions to 7,170.

Major sections of the budget still not confronted by the board, which holds another budget meeting tonight, include administration and maintenance.

The board is scheduled to finish its work on the budget at tonight's meeting, but observers say that the work that still remains may force them to schedule another budget session.

A printed copy of the Board-approved budget must be delivered to the County Council by March 1.

On Tuesday, the day following the Board's budget deliberations, County Council president John Menke called the superintendent's proposed budget "amazing, if not incredible."