School-age children infected with the virus that causes AIDS should be allowed to attend school or day-care programs, but younger infected children should be kept out until more is known about how the disease is transmitted, according to guidelines published yesterday by the federal Centers for Disease Control.

The CDC also recommended that adoption and foster-care agencies administer AIDS antibodies tests to children whose parents are at high risk for the disease, and to children whose parents' history is not known, before placing the children in foster homes.

The guidelines for AIDS, or acquired immune deficiency syndrome, though not law, are the only such national standards, and were developed with representatives from state and county health departments and school officials from around the nation.

They also contain the most detailed advice to date for school systems, day-care centers and adoption agencies dealing with the growing number of children who have AIDS or are at risk of developing it.

Of the 12,599 reported cases of AIDS in the United States, 183 have occurred in children under 18, according to CDC figures.

Children with AIDS have been reported from 23 states, the District of Columbia and Puerto Rico, with 75 percent residing in New York, California, Florida and New Jersey.

The number of children with AIDS is expected to double in the next year, and health officials believe that, as is true in adults, many children infected with the AIDS virus may have only mild illness or no symptoms, and therefore are not reported as cases.

If children with milder forms of the illness were counted, the total "would be at least twice" the 183 reported cases, "if not 10 or 20 times that," said Dr. Martha Rogers, an epidemiologist with the CDC's AIDS branch.

In making recommendations, CDC officials considered both the risk that a child with AIDS might more easily catch infectious diseases in a school or day-care center, and the potential but unknown risk that the child might pass the AIDS virus to other children.

Because there is no evidence that school-age children with AIDS can transmit the virus by casual contact, the CDC concluded that the benefits of attending school would outweigh the risks. But it recommended that each case be considered individually.

Preschool children and some neurologically handicapped children with AIDS should be treated differently because they may lack control of body functions or may be more likely to bite other children, the CDC said.

Such children should be cared for in "a more restricted environment" to prevent exposure of other children to blood or body fluids, it said.

Other recommendations include:

*Those caring for children infected with the AIDS virus should be aware of modes of possible transmission, and wash hands thoroughly after exposure to body fluids (in changing diapers, for example) and before touching other children.

*All schools and day-care centers should adopt routine procedures for handling blood and body fluids, including using disposable towels and tissues when possible and disinfecting soiled surfaces.

*Blood tests to screen for AIDS antibodies should not be required for school entry.

*Doctors, school officials and others dealing with infected children should respect each child's right to privacy, keeping records confidential and trying to minimize the number of people aware of the condition.

Rogers said 80 percent to 90 percent of children with AIDS are under school age, but many need foster care or day care, creating dilemmas for placement agencies.

"Many of these children come from homes where one or both parents are drug users . . . and have problems taking care of the children," she said. In addition, "many of the parents themselves have AIDS and die, leaving the children with no one."

Since foster parents will be expected to make medical decisions affecting a child with AIDS, and to consider the effect of the illness on the rest of the family, the CDC suggests that placement agencies use the antibodies tests to screen children of high-risk parents. Rogers said such tests should also be considered for children whose background is unknown.

Seventy percent of children with AIDS acquire the virus from an infected mother while still in the womb or during birth, and most die of the disease before reaching school age. About 20 percent of cases occur in children who are infected via blood or blood products, and some of these have already forced school and health officials to make difficult decisions.

Two 7-year-olds with AIDS sought to enter the public school system last year in New York, according to a spokesman for the city's Board of Education. Both were offered home instruction by licensed teachers, and accepted it. A third child, 5 years old, was also offered home instruction, but the teacher arrived at the home for the first lesson only to learn that the child had died, the spokesman said.

In Los Angeles, a 3-year-old with AIDS and a speech disorder applied to a program for disabled preschool children, according to Dr. Betty Agee, a county health department official.

Agee said program officials refused to take the child, and "the family went along with it" rather than face other parents' resentment.

The CDC also published precautions for eye specialists to prevent possible transmission of the AIDS virus through tears.