The Fairfax County school system is violating state and federal law by segregating students with certain disabilities instead of placing some of them in regular classrooms, according to a complaint filed by a state agency.

The complaint was filed by the Department for Rights of Virginians with Disabilities, which is charged with protecting the rights of the state's disabled children and adults, and it will be investigated by the Virginia Department of Education.

The disabilities agency said that Fairfax school officials routinely send students with moderate mental retardation to special centers instead of analyzing their individual needs and striving to place as many of them as possible in regular classrooms at neighborhood schools.

"We maintain that Fairfax County has a system where the nature of the disability determines where you are placed," said Susan Ferguson, the agency's director. "Students are primarily placed into the most restrictive environments and segregated from their . . . peers."

Fairfax school officials vehemently denied the claims and said that they have made significant progress in the last two years on a long-term goal of moving all children with disabilities into their neighborhood schools and putting more of them in regular classes.

"It was very disconcerting to hear the charges, and I don't think they have any merit," said Alice M. Farling, assistant superintendent for student services and special education. "We have worked very, very hard--especially in the last two to three years--to build very inclusive schools."

The complaint by Ferguson's agency is based on claims by four families but was filed on behalf of all moderately retarded students in the Fairfax school system.

Ferguson said her department spent 14 months investigating the claims and brought in an outside expert who evaluated the four students named in the complaint and who concluded that their school assignment was inappropriate.

Federal law requires school districts to educate disabled students in the "least restrictive" environment possible, a guideline that sometimes has been interpreted differently by school officials and advocacy groups.

The law also requires school systems to develop an "individual educational plan," or IEP, for each disabled student, with input from parents, teachers and other staff.

Gary Conover, staff attorney for the Virginia disabilities agency, said the agency's investigation found several instances where such plans were developed without parental input or proper evaluation of students' needs.

In one case, Cynthia Barbieri said that when her family moved to Fairfax in 1998, she was not allowed to register her daughter at her neighborhood school because the girl has Down's syndrome. Barbieri said the school district refused to even look at the IEP that had been written for her daughter at her previous school in Connecticut, where she was in regular classes.

According to Barbieri, a Fairfax school official told her to visit a special program at Lake Braddock Secondary School and said, "That's where we send all of our moderate mentally retarded kids."

In another case, the parent of a child with cerebral palsy allegedly was told by a school official, "We have places where kids like yours go, but not here."

Farling said she was not familiar with the individual cases cited in the complaint, but she added, "I know the staff people involved, and I can't imagine any of them saying those kinds of things."

Currently, about 81 percent of the district's disabled students attend their neighborhood school, and nearly all of those students receive at least some instruction in regular classrooms, Farling said.

Superintendent Daniel A. Domenech has said that putting more students with disabilities in regular classrooms at neighborhood schools is one of his priorities, and the School Board will discuss setting numerical targets for that when it holds its annual retreat this weekend.

Farling said the school system has prevailed in similar complaints filed with the U.S. Department of Education's Office of Civil Rights.

Fairfax will have an opportunity to file a response to the new allegations. If the Virginia Department of Education finds that the charges have merit, it will require Fairfax to file a plan for corrective action.