The superintendent of the Fairfax County, Va., school board was ordered to devise a policy on students and teachers who have AIDS. The action came in response to a lawsuit on behalf of an unidentified 5-year-old girl who has been barred from class since Nov. 2 because she has AIDS. It asks that the girl immediately be reinstated and that the nation's 10th-largest school system adopt a policy regarding the deadly disease. "The only thing that we did was to direct (the) staff to come up with a proposed AIDS policy," a board member said. Other school systems nationwide--some under court order--have allowed students with AIDS to attend class. The federal Centers for Disease Control recommended two years ago that most children with AIDS be allowed to attend school.