Washington area schools will get a $16 million windfall if Congress approves the recommendation of a House education subcommittee to increase impact aid to local school systems instead of reducing it as proposed by the Carter administration.

HEW Secretary Joseph A. Califano Jr. last month proposed eliminating from eligibility for the federal benefits children whose parents work on U.S. property outside the country in which they live. That plan would have reduced current aid under to the program by about $13 million in the Washington area.

Instead, the House Subcommittee on Elementary, Secondary and Vocational Education voted last week to restore to eligibility children whose parents work on federal installations outside their home states.

Rep. Herbert E. Harris II (D-Va.) said that while the subcommittee action is "just the first round, it puts us in the position to argue about whether out-of-state aid should be restored, rather than whether out-of-county aid should be out.

"It's good news for taxpayers," added harris, who said testimony provided to two subcommittee members at a hearing in Alexandria two weeks ago played a part in the decision to restore the aid cut four years ago.

When Congress eliminated the out-of-state benefits in 1974, the action was known as the "Montgomery County amendment," because it removed from eligibility 14,000 of the 26,000 children of federal workers who live in that county. Conversely, Montgomery would be a major benefactor by $3.2 million more than it now gets if the eligbility is restored.

The idea of impact aid, enacted in 1950, was to ease the burden imposed on some local school districts by the presence of the federal government, which does not pay taxes on its property. The property tax is the main source of funding for schools. Over the years, presidents annually sought to reduce the scope of the program, largely because so much of the money goes to the wealthy Washington suburbs.

Montgomery County was severely affected by the 1974 cutback because so many of its federal employes work in the District of Columbia. The Carter proposal would hit hardest at Northern Virginia schools because many federal employees who live there also work in Virginia, but cross county lines to work at huge installations such as the Pentagon in Arlington and Fort, Belvoir, in Prince William County.

The subcommittee recommendation would nearly double Montgomery's share in the program, from $3.7 million to $6.9 million. The Carter plan would have cut the aid to $2.6 million.

Fairfax County would be the biggest beneficiary in dollars, qualifying for $17.8 million, compared to $13 million in the current fiscal year. Fairfax would have been the biggest loser under the Carter plan, which recommended $8.9 million.

Here's how other area school systems would fare under the subcommittee plan, as compared to the current payments, the first figure in parenthesis, and the Carter proposal the second figure in parenthesis:

District of Columbia, $7.4 million ($5.2 million and $3.9 million); Alexandria, $1.9 million ($1.1 million and $835,000): Prince William County, $2.7 million ($2.3 million and $1.6 million); Loudoun County, $690,000 ($475,000 and $328,000); Prince George's County, $11.6 million ($7.8 million and $5.3 million).

When he appeared before the committee on Feb. 28, Califano acknowledged that he was participating in "an annual rite of spring" in which representatives of the president "march up Capitol Hill with a broad proposal to reform Impact Aid and march down the Hill in the summer without it."