Prince George's County School Superintendent Edward J. Feeney told principals yesterday they must notify him today what jobs they are prepared to sacrifice when layoff notices go out next week to 400 teachers and 500 other employes of the beleaguered system.

At a meeting with 400 administrators, supervisors and principals at High Point High School, Feeney asked his top aides to "rise to the occasion" necessitated by massive budget cuts approved Wednesday by the County Council.

Feeney distributed to each principal a sheet showing the number of positions each school will lose this fall because the budget approved by the council, at the recommendation of County Executive Lawrence J. Hogan, was $31 million less than the school board said it needed for fiscal 1983.

Hogan continued to insist yesterday that layoffs are unnecessary. He said the school board should refuse to fund fully the teachers' negotiated contract, which calls for a 6 percent cost-of-living increase this fall.

At yesterday's subdued gathering of school administrators, Feeney said, "I want you to be sympathetic and understanding with these people on your staffs who will not be returning. It is a terrible time to be unemployed." Feeney urged the principals to take phone calls in the night to help the expected victims of the unprecedented layoffs.

The grave speech received no applause from the administrators, who sat in stony silence and asked only a few questions before quickly leaving.

"People are kind of stunned, numbed, trying to pick up the pieces," said Dora Kennedy, a supervisor of foreign languages. "I think he's right. We have to pick up and press on."

The administrators were told to indicate which subject classes--but not names of employes--would be cut. School staffs will then order the list of teachers and other employes within each area of qualification by seniority to determine who will be laid off.

"It is enormously complicated to identify the individual who's going to be riffed," said Assistant Superintendent Edward Felegy. "We think we've identified the basic individuals, but there's a lot of fine tuning to be done."

Feeney and his staff said they are trying to hold down the number of rifs by cutting expenditures in all areas. The cuts are designed to be more broad than deep, affecting every area in the schools from textbooks to buses. For example, Felegy told the audience that 1,900 elementary and 1,300 secondary school students will lose bus service.

"I think the biggest thing is personnel," said Ronald Hillard, principal of Bradbury Heights Elementary School, as he flipped through the eight-page list of cuts.

"Long range, I'm going to have a difficult time maintaining the building because so many of the cuts are in maintenance. Mine happens to be a very old building," he said.

Hogan issued a prepared statement yesterday saying, "I knew the 1,500 layoff figure released by council staff two weeks ago was not accurate. Within two weeks, that number has dropped to 900. Again, I don't believe that number is realistic. If the board acts responsibly, there will not have to be layoffs."

The executive, who is a Republican candidate for the U.S. Senate, has said that the 6 percent pay raise should be pared to 3 or 4 percent, and negotiated dental and tuition assistance plans dropped, bringing teachers' wages and benefits into line with those of other county employes. The budget approved this week gives county employes a 7 percent pay increase, but Hogan pointed out that last year school employes got a 10 percent increase, compared to 7 percent for county workers.

Hogan also continued to maintain that normal turnover rate, along with a lower pay raise, would prevent layoffs. School officials continued to deny that attrition is as high as Hogan has claimed.

"It's not simple mathematics," said Carl McMillan, director of professional personnel for the 11,600-employe system. "If a physics teacher leaves, you can't replace him with an elementary teacher . . . .You're talking about different categories of positions."

McMillan said turnover among professional staff is running at about 8 or 9 percent, but some of those leave over the summer so there is no way of knowing what subjects will be vacated by attribition until fall.

Robert Glickert, director of classified (nonteaching) personnel, added that while attrition in some of his departments has run as high as 15 percent yearly, the turnover rate has slowly dropped over the years, and the more skilled employes are far less likely to quit.