The Arlington County school board has adopted a $45.3 million budget for fiscal 1978 that falls just within the county board's limits on school spending.

The new budget, $2.4 million less than Supt. Larry Cuban's proposed budget of $47.7 million, restores some new programs and services cut from the school system this year and adds some new ones. It also provides "modest salary increases" for school personnel, according to board chairman Diane Henderson.

The budget will go to the County Board for funding in early April.

"The school board feels that this is a good budget, allowing for a solid educational program, within the constraints given," Henderson said. What she calls constraints are inflation and the rising cost of living, tha tclimb faster than available school funds.

Cuban earlier had said any budget that fit within the county guidelines for school spending "would severely damage our schools." The county guidelines range from $43.3 million to $45.3 million.

However, since the school board's budget eliminates two major expenses provided for in Cuban's recommended budget, an additional $1.5 million becomes available for school spending.

Oneof the expenses the school board will propose the county pay is $988,000 in salaries to cover an extra payday that falls in fiscal 1978.

Henderson says the County Board in 1968 required the school board to pay salaries from its fiscal 1969 teacher salary account, giving the county a windfall of between $2 million and $3 million that the County Board used to balance its own budget. At the same time, the County Board also required the school board to change from a monthly to a biweekly pay schedule. If the school system were still on a monthly pay schedule, Henderson said, the extra payday would not have fallen in fiscal 1978.

"We feel this matter of salaries is not part of the budget, and we will negotiate the matter separately with the County Board," Henderson said. "We are taking the approach that since it was County Board action that led to the extra payday this year, it is fair to ask them to pay."

The other expense that the school board has omitted from its budget is a $600,000 repayment of a loan from the County Board.The school board plans tto ask the county if the loan can be repaid after this fiscal year.

The school board lowered Cuban's recommended budget mainly by chipping a little from several school accounts rather than cutting a great deal from any one area. The major cuts made to the superintendent's budget, and this year's school program, were the elimination of sabbatical leave for teachers, a fund that totaled $90,000, and reducing the employee schoolarship fund from $70,000 to $45,000.

The school board earmarked $860,000 for salary increases. Although the money has not been distributed among teachers and other personnel, Henderson noted that it is less than in previous year.

"We regret we can't offer employees more now as we have in the past and hope to in the future," Henderson said.

She added that "teachers will benefit by having essential services restored and by maintaining the current pupil-teacher ratios of 19.5 to one in the secondary schools and 26 to one in the elementary schools.