After a long series of votes and maneuvers, the Fairfax County School Board last night settled on a new, more conservative leadership and, in a surprise move, prohibited in-school fund-raisers throughout the Fairfax public school system.

Although the unanimous selection of Dranesville member Mary E. Collier as chairman came early as expected, behind-the-scenes politicking delayed until almost midnight the election of Mount Vernon representative Gerald A. Fill as vice chairman. Collier, a former teacher, and Fill, a management analyst for the Office of Management and Budget, both described themselves as moderately conservative.

The proposal to ban charity drives, which had been discussed and tabled by the board several times in recent months, was added to last night's agenda at the last minute by Superintendent William J. Burkholder.

Burkholder, who has strongly supported the ban, submitted an alternative proposal that would have allowed each high school to participate in one charity drive per year. Elementary and intermediate schools would have been prohibited from any fund-raising activities for outside organizations.

Burkholder told the board that although the new proposal was "just the most desirable of alternatives," he recommended that the board vote to extend the ban to high schools.

Outgoing chairman Ann Kahn agreed to support the ban, saying a recent poll of teachers indicated that their frustration with additional duties, such as collecting money from fund-raisers, was second only to their concern over the question of merit pay.

The board's vote was 6 to 4 in favor of the total ban.

Although Virginia state law forbids door-to-door solicitation by elementary school students, school administrators estimate that last year, elementary pupils raised $200,000 for Fairfax County charities.

Collier, 41, is a resident of McLean and a former teacher in Raleigh, N.C. She has served as president of the Chesterbrook Elementary School PTA and on the Capital A Area III task force on declining enrollment.

Dranesville, the county's second largest district, has both an area of declining enrollment, near the Capital Beltway, and a growth area to the west.

Collier has indicated that the completion of the county-wide declining enrollment study and a system of performance pay for teachers will be two of her major concerns as chairman.

Before the election, Collier was described by her fellow school board members as able and well-liked. Dranesville supervisor Nancy Falck, whom Collier succeeded on the school board in December 1979, called Collier "open and available," a woman who "does her homework."

Collier served for the past two years as vice chairman under Kahn, who announced that she would not seek reelection because of her new position as vice president of the National Congress of Parents and Teachers.

Fill, one of four candidates for vice chairman, eventually gained eight of his colleagues' 10 votes by isolating more liberal Centreville representative Carmin C. Caputo and winning the support of the other two candidates, Anthony Lane and Toni Carney.