The Montgomery County School Board's conservative majority began implementing its back-to-basics philosophy yesterday by tentatively agreeing to cut administrative positions and to provide more money for textbooks and additional teachers.

In its first action session on the 1980-81 school budget, the board's four-member majority shaved about $200,000 from Superintendent Charles M. Bernardo's $287.7 million budget recommendation. That action came in an effort to meet a County Council request for a 3 percent ceiling above the 1979-80 budget.

The majority voted in the 11-hour meeting to increase spending for textbooks and teachers by $1.1 million, while reducing administrative costs by $1.3 million. For the first time, the board also established strict limits on the size of classes.

In effect, the majority -- President Marian Greenblatt, Joseph Barse, Eleanor Zappone and Carol Wallace -- began fulfilling election pledges to refocus the school budget on the classroom. In doing so, they announced tentative plans to scrap an expansion of the schools' controversial computer instruction program and to cut costs in each of the administration's five area offices by $200,000.

The board majority campaigned last fall on the theme of redistributing the school budget by allocating more money for instruction and less for administration. The majority also promised to bolster teacher morale which it said suffered in the last decade amid untested computer instruction programs, oversized classes and insufficient supplies.

The board tentatively agreed yesterday to:

Add 72 teachers throughout the system.

Drop 38 assistant principals, teachers' aides and serctetaries.

Purchase almost $500,000 in additional textbooks.

Limit classs size to 28 pupils in grades 1-3, 30 in grades 4-6 and 32 in secondary school classes.

The four members of the majority supported these changes and, in individual cases, were joined by members of the minority.

Minority members Blair Ewing and Daryl Shaw protested that the establishment of class size limits was a matter of school policy and should be reviewed and debated outside of a budget meeting. Ewing voted in favor of the class size ceilings, but said the action is a violation of board policy.

At one point, after the board members finished combing through the elementary school section of the budget and began to dig into junior high school areas, Ewing shook his head and declared to the majority members, "It's utter nonsense to think you can run a school by adding teachers and reducing administrators and secretaries."

Shaw protested the cuts in assistant principals, saying "I worry about this move. You don't seem to realize how important a job assistant principals perform in helping out and managing teachers."

During discussion on class size Barse, quoting a University of Colorado study on the issue, said, "I clear and strong relationship between class size and achievement has emerged. There is little doubt that... more is learned in smaller classes."

Current class size in county elementary schools averages 26.5 pupils, but Wallace cited school statistics showing over 30 elementary school classes with as many as 35 pupils. More than 200 senior high school English classes, she said, have more than 35 pupils.

"It's time the issue was addressed," she added.

The majority members said they hope that each child in the system will be able to have a textbook in every subject without having to share.

A final vote on the 1980-81 school budget is expected Monday. The budget is scheduled to be reviewed by the county council March 1.