The Fairfax County School Board, in a decision that the school superintendent said could have farreaching implications, voted last night to allow 15-year-old Sandra (Sandy) Doty to try out for the hitherto all-male McLean High School baseball team.

By a 7-to-3 vote, the board, reversed a decision by school administrators who had argued that girls should play softball.

Superintendent S. John Davis said the decision means that girls can play baseball and boys can play softball and athletic directors fear that boys will take over the softball teams from the girls. Girls are still ineligible to participate in contact sports such as football.

Sandy, a right-handed sophomore who likes to play second base, apparently will be the first girl in the Washington area and in Virginia to be allowed to try out for a high school baseball team, according to Fairfax County school spokesman, George Hamel.

School administrators, including Davis, had denied Sandy's request to try out for the baseball team because of a school policy that permitted only boys to play baseball.

Last night the school board heard Sandy's appeal.

She stood nervously at the podium and told the board that under provisions of a 1972 amendment to the U.S. Civil Rights Act she cannot be denied permission to play baseball.

"I know girls are supposed to play softball," Sandy said. "But, I want to play baseball.... I think I can work just as hard as the guys."

After a closed 25-minute session in which board members discussed the case, the board reconvened to announce its 7-to-3 decision.

Board member Ann Kahn, who introduced the motion to permit Sandy to try out for the baseball team, said the majority agreed that Sandy has a constitutional right to try out. "Her aspirations should not be limited," Kahn said.

In addition to Kahn, voting to allow Sandy to try out were board members Toni M. Carney, Robert E. Frye, Robert E. Smith, Anthony T. Lane, Nancy Falck and Gary Jones. Opposing the measure were school board chairman Rodney F. Page, J. Roger Teller and Ruth Dell.

"I'm so glad it's all over with," said a jubilant Sandy, whose skills have earned praise after she played on a team that won the McLean Little League baseball championship and on other teams.

Last night she hugged her father, Chet Doty, and said, "Now I can start practicing. I'm going to get my glove out and practice hard."

As for the future of girls' softball at McLean High, Cricket Call, the girls' athletic director there, said three boys signed up for that team yesterday.