The Fairfax County school system doubled its hiring of minority teachers this school year, but still failed to meet its affirmative action goal, the School Board was told last night.

The annual affirmative action report, presented to the board by Assistant Superintendent Edward Carr, showed the school system met eight of its 15 goals for hiring and promoting women and members of minority groups.

That represented a slight improvement over last year, when seven goals were met.

A stepped-up campaign to hire minority teachers helped achieve improvements -- 15 percent of this year's new employees were minorities, compared with 7.6 percent last year -- but the results still fell short of the 18 percent goal. Among other steps, school system recruiters visited more black colleges, made more on-the-spot job offers and worked with more community groups representing minorities than in the past, Carr said.

"I'm happy for the results achieved this year versus the results last year," said board member Frank Francois, a black who was appointed to represent minorities. "While there is still room for improvement, significant gains have been made."

The school system achieved three of its four goals for hiring and promoting administrators, two of three goals for maintenance workers, and its goal for hiring minority bus drivers. Also met were goals for hiring minority and male clerical workers.

But the school system failed to meet goals for food service and professional-technical workers, and all three goals for food service workers.

In other business, the board agreed that it will adopt a policy May 12 on students and teachers with AIDS after a report from an advisory committee March 23 and a public hearing April 19.

Most of the 41 advisory committee members, who were named by the superintendent, board members and community groups, were announced last night. The committee chairman is Ann P. Kahn, a former national PTA president and county School Board member.

The board had resisted adopting a written AIDS policy, but changed its mind after the mother of a 5-year-old girl with AIDS who had been removed from class filed suit to require the child's return to school. A policy proposed by the superintendent would name a committee to evaluate the medical evidence in each case.

The board postponed until next Thursday a vote on its five-year annual capital improvement plan, which would allocate $491.7 million to open five new schools and repair dozens of others by 1993 because of population growth and aging buildings.