Montgomery County school board members faced questioning ranging from how many janitors will be needed to whether the school day should be shortened in 12 high schools as it grappled with the 1980-81 school budget last week.

When all the questions were answered, the board voted 6-to-1 to approve tentatively a $314 million budget that would:

Maintain current class sizes, which range from a suggested maximum of 26 children in a kindergarten room to 32 students in a high-school class.

Provide the same amount per pupil as this year for textbooks, ranging from $5 for kindergarten pupils to $20 in the higher grades.

Add no instruction programs.

Expected cutbacks in federal and state aid, coupled with soaring utility costs and teachers wages have pushed the budget to $314 million, $16 million over the figure recommended by the County Council.

This would require homeowners to pay from $50 to $60 more in property taxes, County Council member Neal Potter estimated.

Final school board action on the budget is scheduled for today. County Executive Charles W. Gilchrist next tackles the complex budget before it goes to the County Council, the body that will decide in May how much Montgomery's 185 schools will have to spend next year.

Armed with draft budget volumes as thick as "Gone With the Wind," the school board last week plowed through every page of figures proposed in December by (then interim) Superintendent J. Edward Andrews.

Although the board made few changes in Andrews' austere budget, tax-conscious county officials vow to scrutinize it in coming months. Several council members predict unusually tough sessions ahead as they try to bring the figure closer to the $283 million they planned for schools in the county's overall $608 million budget.

"Enrollment keeps going down, yet school costs keep going up. Taxpayers are very concerned about that," said council member Michael Gudis.

Andrews, in fact, counted on a projected decline of 5,000 students to eliminate 241 positions from the system. In addition, $500,000 will be saved by closing one junior high and three elementary schools at the end of this academic year.

County schools serve 102,000 students this year and expect 97,000 next year, a steep drop from the county's enrollment of 126,000 in the mid-70s.

Closing schools, however, means busing more students to schools further from their homes at a time when gasoline prices are skyrocketing, school officials point out.

Rising costs prompted Andrew to ask for a $1.8 million increase in the $10 million schools now pay for heat, light and other utilities.

More state and federal laws requiring schools to educate handicapped children added another $1.3 million to Andrews' tally. The school system now pays private school costs for about 750 handicapped youngsters who cannot be accomodated in county schools, according to school budget director Ken Hill. In addition, Andrews added 54 staff positions for special education, while cutting 290 positions because of declining enrollment.

But the biggest budget leap of all the result of pay increases demanded this year by county teachers and staff members whose three-year contracts will expire in July.

Inflation again was blamed for making Montgomery County teachers the most poorly paid among those in school districts around the Beltway. The system and the teachers, who had been at an impasse in contract negotiations since December, finally reached an agreement last week.

Under the new two-year contract, teachers will receive a 10 percent pay raise next year and a minimum increase of 7 percent the following year, or 75 percent of the cost of living increase.

"It's not everything we asked for, but it is a step towards a better contract," commented one negotiator.

As teacher salaries and utilities rise, revenues from state, federal and other noncounty sources is expected to drop by $2.4 million for the 1980-81 school year. The biggest reduction is an anticipated 50 percent cut in federal impact aid, which the county receives for educating offspring of federal employes.

Although Andrews attempted to cope with rising costs and decreased aid, he fired off an angry letter to the County Council last month. In it, he blasted the council for holding schools to a 5.9 percent budget increase while permitting the county government a 12.5 percent increase. b

Andrews criticized the council for its "erroneous assumption" that school costs drop at the same rate as enrollment. "I believe the method used to set this budget target of 5.9 percent is unrealistic and discriminatory, and. . . it will be impossible to meet," he wrote.

Council President Scott Fosler has not responded to Andrews' letter yet, but said in an interview, "It's a difficult position for the council to be in. On one hand, we're trying to provide good education. On the other hand, we're concerned with costs and taxes."

The unusually swift vote that left his budget virtually intact were a victory for Andrews, who recently accepted a four-year appointment as superintendent after months of refusing the demanding post.

Andrews successfully persuaded a majority of the board members to defeat a measure proposed by Marian Greenblatt to cut at least one of the school system's five administrative offices. That cut would have saved anywhere from $250,000 to million dollars, it supporters claim.

Andrews also pushed through a cost-saving measure that drops a seventh classroom period in 12 of the county's high schools. The seventh period was intended to provide a broader range of subjects for students in the smaller schools, which will now have six class periods as do the other nine high schools in the county.

Board liberal Blair Ewing and conservative Joseph Barse both opposed that measure.

The $750,000 Andrews saved there, however, is offset by $690,000 in additions to programs like bilingual and drug abuse education.

"There's a honeymoon flavor to all this," said Barse, who was the only board member to vote against Andrews' budget. "They're still under the Ed Andrews magic."

Barse conceded there was little to cut in Andrews' budget but he said, "The total is still too high." CAPTION: Chart, shows daily costs per pupil for the 1979-80 school year. Montgomery's tentative budget for 1980-81 projects an overall $31 million increase in school costs. The Washington Post