The Prince George's County Board of Education scheduled three unpaid furlough days for nonprofessional personnel last night, affecting about 3,700 custodians, bus drivers, teacher aides and maintenance workers.

The furlough days were part of an agreement reached between the board and representative unions last June to avoid the layoff of 312 members of ACE-AFSCME local 2250 and Supporting School Service Employees Local Union 400. The unions also agreed to postpone negotiated pay raises for most of the current school year.

At that time union leaders received assurances from County Council members that funds would be provided if they became available to end the need for the furloughs.

"We're still hoping that by April we'll get some help," said Local 400 president Carnell Reed, whose 1,020 members will get their first furlough day on March 31. "But I can't really say if it will come."

The Prince George's teachers union refused to make similar contract concessions when the school budget was cut last year, forcing the layoff of 507 teachers. Reed said his members would not choose the job-saving furloughs today.

"The building service workers could not afford to give concessions again because we live from payday to payday." Reed said.

The school board also approved a 1983-84 school calendar last night that lacks, for the first time in three years, a school day off for observance of the Jewish holy day of Rosh Hashanah.

Board member Leslie Kreimer opposed deletion of the Sept. 8 holiday from the calendar proposed by Superintendent Edward J. Feeney, saying the board was insensitive to the needs of teachers and students of the Jewish faith.

Board members said they supported the change because Rosh Hashanah would have been a second day off during the second week of the new school year, which also contains Labor Day. In a heated and emotional discussion, they also said they understood that Yom Kippur, to be observed Sept. 17, is a much more important holiday in the Jewish faith and more worthy of recognition.

The resolution by which the calendar was adopted, proposed by board member Norman Saunders, recognized Yom Kippur as the highest of Jewish holy days and declared the board's intention of making it a day off if it occurs during the week. Yom Kippur falls on a Saturday in September this year, requiring only a rescheduling of athletic events, according to school staff.

"It gets them off the hook for this year," said Kreimer, who is Jewish, referring to the resolution. "They obviously did not want to do it [close schools on Rosh Hashanah] this year so they used a side maneuver." She said that in past years the schools were closed on one or the other of the holidays if they fell on a normal school day.