Proposals for trims to Prince William County’s budget, along with cuts in federal and state funding, have school officials increasingly worried about what budget slashing might mean for students and teachers.

If the county adopts the advertised real estate tax rate of $1.196 per $100 of assessed value, it would mean the school superintendent’s proposed budget would have to trim at least $1.3 million. The Board of County Supervisors can lower the advertised rate but not raise it.

At the high end, that rate would mean an increase for many homeowners: slightly less than the average 4 percent increase to $3,449 recently proposed by County Executive Melissa Peacor.

Initial reports from the recently passed state budget show that the region’s “cost to compete” funding has been slashed to the tune of $4 million per year, school spokesman Philip Kavits said. Those funds are allocated to Northern Virginia jurisdictions to pay personnel more because of the higher cost of living than in other parts of the state.

All told, Superintendent Steven L. Walts’s proposed $893.5 million operating budget, an increase of 3.2 percent over last year, will have to be cut by at least $5 million, Kavits said. That number doesn’t include any possible effects of “sequestration,” federal cuts that began Friday.

The school budget now includes a 2 percent pay raise for employees. Kavits said the school system has not made any decisions on where the budget cuts should come from.

“There’s been no decisions on that. . . . It will be the subject of discussion going forward,” he said.

Residents can weigh in on the budget during a hearing March 20 at the Edward L. Kelly Leadership Center.

Walts said in a statement that this year’s budget negotiations are particularly challenging.

“The sequester will deal a particular blow to funding that serves children with some of the greatest needs, those in poverty and our special-education students. We have not calculated specific dollar impacts yet, but they will be large and potentially devastating,” he said. “Our budgets have already been cut to the bone, but we will do everything necessary to keep Prince William County public schools delivering the quality education our students deserve and our community expects.”

The number battles belie what students and parents feel: Crowding, particularly in western Prince William, is prevalent. The school system has the largest class sizes in the state and spends the lowest amount per student of any jurisdiction in Northern Virginia.

Some parents have complained about the board’s priorities in recent years, including expensive schools and amenities, such as a swimming pool proposed for the mid-county high school, scheduled to open in 2016.

The school system “continues to have champagne taste on a beer budget, opting for award-winning architecture and amenities rather than award-winning test scores and graduation rates,” parents Tracy Conroy and Dyanne Liga of the group Our Schools have said in a statement.

School Board Chairman Milton C. Johns (At Large) said that “layoffs and furloughs should be the very last resort.” Keeping up with costs in a school system slated to have about 2,000 new students next year is difficult, he said.

Johns said he is skeptical of the proposal from Supervisor Peter K. Candland (R-Gainesville) that would keep average real estate tax bills flat while offering up to an additional $50 million for programs that would reduce class size and increase teacher salaries.

“I’ve never seen any magic like that before, and if he could pull it off, it would be pretty amazing,” Johns said. “It’s very difficult to make something like a flat tax bill work when you’re in a community with a growing school system and state and federal requirements to educate students. We don’t have the option of cutting out a couple of middle schools.”