Fairfax County school officials last night proposed severing Fort Belvoir from the county school system in order to shift the financial burden of educating the 2,000 students living on the Army base to the federal and state governments.

The proposal came less than a week after the Justce Department filed suit to block the county from charging tuition for the children who live on the base and attend three schools now operated by the county there.

It is the latest in a series of attempts by the school board to offset potential cutbacks in the federal program, called impact aid, for subsidizing the cost of educating children of employes living on federal installations. The board will vote on the proposal at its Nov. 19 meeting.

School officials said they could lose an estimated $4.4 million in impact aid allotments under budget proposals pending in Congress. They said establishing Fort Belvoir as a separate school district would protect the board from annual threats of budget reductions.

"It's become obvious that impact aid will continue to be cut until the whole program is cut out," said John Hess, director of financial services for the school system.

School board member Carmin Caputo cautioned that severing Fort Belvoir from the county system "looks like too neat a solution."

The plan would have to survive a long political route before it could be implemented: approval by the school board, the county Board of Supervisors and state Board of Education. The Virginia General Assembly has final veto power over such a proposal.

The Justice Department suit contests the board's original proposal to charge tuition ranging from $2,600 for elementary schoolchildren to $16,330 for a severely retarded youngster.