As many as 51 teachers and 97 aides could lose their jobs next fall if the County Board decides this Saturday to ahdere to its own spending guidelines and trim the county school budget by nearly $3.4 million.

In addition, another 122 teachers could lose their jobs depending on the amount of federal aid the schools receive this fall.

At the meeting, scheduled for 8 a.m. Saturday at the courthouse, the County Board, facing a May 1 deadline, is expected to approve the final county budget for the fiscal year that begins July 1. As currently proposed, school expenditures make up nearly 30 percent of the total $149 million in county expenditures for the new fiscal year.

Since the school budget was first proposed this winter, County Board members repeatedly have said they want to limit the county contribution to the budget to $43.5 million, nearly $3.4 million less than requested by the school board. The total budget proposal for the schools is $60 million.

"We've been pretty clear as to where we are," County Board member Walter Frankland, a vocal critic of school spending, said this week. "Nothing's been done to make it a realistic budget."

But Frankland and board chairman Stephen H. Detwiler, both members of the GOP majority on the board, declined to predict the final outcome of the budget battle. The board, Frankland said, has questions about the $1.5 million deficit in the current fiscal 1981 school budget that need to be answered before final action is taken on the fiscal 1982 school budget.

However, board member John G. Milliken, a Democrat, noted that the schools had higher than expected enrollment and fuel costs. "It is clear to me that a figure substantially higher than (the recommended $43.5 million) is justified."

If the cuts are approved, pay raises for teachers could be limited to 6 percent instead of 9 percent recommended by the school, and at least 51 teachers, including 43 full-time employes, and 97 aides could lose their jobs. On April 9, those teachers received "reduction in force (RIF)" notices, telling them they may not be rehired.

RIF notices also were sent to another 122 teachers, including 85 full-time instructors, on April 3. Those notices, according to Director of Personnel Henry Gardner, are sent to a number of teachers each year to protect the county in case it loses federal funds. Teachers with the least seniority are told they will be laid off first. However, most of the teachers will get their jobs back once the county has firm figures on the amount of federal aid it will receive.

"In the past," Gardner said, "the ballpark figure has been that 75 percent of them are hired back by the beginning of September and more during the year."

Given the uncertainty of County Board action and proposed cuts in federal aid, however, Gardner declined to predict how many of the 122, or the additional 51 teachers and 97 aides, would be rehired.

"If the $3.4 million is taken away, some programs will undoubtedly have to be cut and some positions phased out, but I can't tell which ones yet," Gardner said. He added that some of the 51 teachers who got RIF notices may be rehired before some of the other 122 because of seniority.

By eliminating the 51 teachers and 97 aides, Gardner said, the county could save roughly $1.1 million. But teacher representatives said the attempt to save money could backfire educationally.

Catherine Hartness, president of the Arlington Education Association which represents nearly 900 teachers in Arlington schools, predicted the additional cuts could lead to higher pupil-teacher ratios, fewer electives and possibly fewer after-school extracurricular activities which young teachers, those with the least seniority, tend to sponsor.

"Everybody's very depressed. People are very upset," Hartness said. "It's not likely that those who received the (April 9) notice will be recalled if the budget is cut."

School board Chairman O. U. Johansen sympathized with Hartness, but contended that the school system had to send out as many RIF notices as it did.

"There's a great deal of uncertainty and unhappiness on the part of many teachers," Johansen said. "It's very traumatic to get that kind of notice. . . .

"But we have to RIF for the worst possible eventuality because we can't get caught with teachers the budget won't pay for. The problem is we don't know what the County Board is going to set (as its share). Hopefully, we'll get more than the guideline called for."

Board member Torill B. Floyd maintains that guideline is "unrealistic."

"Unfortunately we had to RIF that many to be on the safe side because we didn't know what the County Board would do," she said. "I certainly hope we will be able to recoup, that the County Board will come in with a (share) somewhere between the guideline and the recommendations we came in with."