The parent of a child who was expelled from a Fairfax County school for having AIDS will file suit today seeking the child's return, the parent's lawyer said yesterday. It would be the first such lawsuit in the Washington area.

The child enrolled in the county school system in August after submitting medical records indicating the presence of AIDS, which the child is believed to have acquired from blood transfusions shortly after birth, lawyer Kenneth Labowitz said.

The child's name, sex and age will not be made public at the request of the child's mother, Labowitz said.

In November, school officials ordered the child out of the classroom, he said, and refused to change that ruling after meetings with a doctor and the parent. The county has not provided home schooling, he said.

The Fairfax County School Board has never adopted a policy on AIDS, but Superintendent Robert R. Spillane has stated that students and teachers with AIDS will not be allowed in the classroom because of a state law barring people with contagious diseases from being in school.

Two years ago, the federal Centers for Disease Control, citing research showing that AIDS is not spread through casual contact, recommended that most infected school-age children be allowed in classrooms without restriction. Only in cases where young children might bite or otherwise draw blood should school officials consider restrictions, the agency said.

County schools spokeswoman Dolores Bohen reaffirmed the Fairfax policy yesterday, but said officials would not comment on the issue until after the lawsuit is filed.

The Fairfax County policy is believed to be among the most stringent in the area. In Maryland, state officials say they know of a dozen children with AIDS currently attending school. Except for the Fairfax child, there have been no known cases of AIDS-afflicted students seeking to attend school in the area.

Acquired immune deficiency syndrome destroys its victims' immune systems, leaving them vulnerable to cancers and other diseases. Most patients are adults, but 729 children in the United States were reported to have AIDS as of Dec. 14. Most are believed to have contracted it from their mothers at birth or from blood transfusions before March 1985, when blood banks imposed tighter screening of donations.

The planned lawsuit to be filed against the county school system in U.S. District Court in Alexandria would be only the fifth in the nation, according to Labowitz. In the other four cases -- two in Florida, one in Indiana and one in California -- federal judges ordered school systems to readmit children who had been sent home because they had AIDS.

One of the federal court cases involved a 5-year-old Atascadero, Calif., child, Ryan Thomas, who was suspended last year for biting a schoolmate. A judge ordered him readmitted.

Labowitz said the lawsuit would charge that the Fairfax child has been denied the right to a free public education under federal law that prohibits discrimination against the handicapped. He said legal papers would seek not only to have the child readmitted and awarded an unspecified amount of money damages, but also to force the county to enact a policy ensuring the education of other students with AIDS.

Labowitz said the child, who is being treated with the drug AZT, is suffering emotional problems because of being kept out of school and "is having a difficult time understanding why school is foreclosed."

"There is no legal or medical reason why the child should not be going to school," he said.