The Fairfax County School Board ended a two-year moratorium on school closings last night amid boos and hisses, voting to shut down seven elementary schools in the eastern part of the county.

The decision, made before a largely hostile crowd of almost 500 at Woodson High School, climaxed six months of study, political pressures and a series of acrimonious public hearings at which angry parents waved placards and presented petitions.

School closings have been an emotional issue throughout the Washington area as enrollments have declined in recent years. But this year's proposal to close as many as eight, elementary schools in Fairfax provoked a particularly sustained outcry from parents in the children who would be affected.

It was almost viewed as traditional that the Fairfax school board would close no more than one school a year.

The closing of the schools was justified by Superintendent L. Linton Deck largely on the grounds that it would improve the quality of education. He said a large elementary school would offer students more flexibility and resources than several smaller ones.

The board went along with seven of Deck's eight closing recommendations, voting to shut down Devonshire, Edsall Park, Hollin Hall, Hollin Hills, Masonville, Walnut Hill and Wilton Woods elementaries at the end of this school year.

Annandale Terrace Elementary, also recommended for closing, was spared because of high enrollment and low per-pupil costs.

Deck was the focus of much of the parents' criticism for recommending that eight schools be closed while citizen advisory groups called for shutting down only three.

Last night's vote was a victory for Deck and climaxed his first controversy since taking office in January.

Those opposed to the closings argued that they would save county taxpayers little if any money.

One school administrator conceded that immediate savings would be minimal, although more would be saved in future years.

Another point of contention was over population projections made by school officials. Citizens in areas with undeveloped land argued unsuccessfully that children from future housing developments would eventually fill empty classrooms.

School board members argued that they had made a commitment to close schools this year and were not going to back down because of criticism.

"The facts are compelling," said member Robert Smith from the Annandale District. "There are hundreds of empty spaces in our schools and some of our students are educationally disadvantaged because of small schools."

Board members, while appointed rather than elected, were feeling political pressure as election-conscious county supervisors made it clear that several school board members could lose their jobs if schools were closed.

Earlier this week, the supervisors voted that the school board should present evidence of significant cost savings before closing any schools.

That message to the school board was the idea of Supervisor Thomas Davis (R-Mason), who made no secret of his disagreement with school board member Roger Teller, who represents the Mason district and was appointed to the board by Davis' predecessor on the Board of Supervisors.

Davis said earlier this month that if schools were closed in his district and parents were unhappy, he would be unable to reappoint Teller when his term expires in June 1981.

Teller voted with the board majority last night to close the seven schools, including two in his own district, Masonville and Walnut Hill.

Only one board member, Anthony T. Lane of Lee District, consistently voted against closing any schools. "Perhaps," he said, "we all should have thought that we might do well to wait a year and get census data."

On hand for the voting was Supervisor Joseph Alexander (D-Lee), an outspoken opponent of all school closings. At the decision to close Wilton Woods Elementary, which is in his district, he stormed out of the meeting.