Administrators for Fairfax County public schools are projecting a $156 million deficit for next year’s budget as the school system seeks to provide teachers and staff with significant raises after years of stagnant compensation.

“It’s not good news,” Susan Quinn, Fairfax schools’ chief financial officer, told board members during a meeting Monday. “We have huge challenges ahead of us.”

Quinn said that the board had depended too heavily on leftover funds from previous years to balance the budget. This year, the board has about $45 million in leftover cash from last year’s budget, but it’s not nearly enough to offset the expected shortfall. Neither are the potential savings outlined in an outside audit that was presented to the board at the meeting Monday afternoon.

About 88 percent of the school system’s $2.5 billion budget goes toward employee compensation. During the recession, the school system eliminated 1,450 positions from the payroll, froze salaries and increased class sizes by one student per teacher, saving about $475 million while trying to spare academic programs. Student fees were increased to make up for lost revenue.

In four of the past five years, the school system did not give significant raises to salaried staff. Compared to other school districts in the region, Fairfax County lags in average teacher compensation, according to the Washington Area Boards of Education guide.

In addition, new School Superintendent Karen Garza said, the average spending per pupil has only increased by 65 dollars since 2008.

Much of next year’s projected deficit is driven by about $65 million in combined increases in retirement funding and health-care insurance rates. Rising enrollment — the school system predicts the student population will reach 187,000 in 2015 — will add about $25 million to the budget, according to Quinn. Employee raises will add another $42.7 million, she said.

“We’re facing some difficult choices here,” said Ted Velkoff (At Large), chair of the school board’s budget committee.