The Los Angeles County Office of Education has violated federal law by isolating dozens of mentally handicapped students in special schools when they could have been educated on regular campuses, an investigation has found.

The U.S. Department of Education's Office for Civil Rights also found that handicapped students at the special schools attended class for less time than regular students in nearby school districts, another violation of anti-discrimination laws.

The county Office of Education has agreed to correct the deficiencies at its so-called "special centers."

"We've started implementing the (improvement) plan," county spokesman Frank J. Tocco said.

Officials plan to re-screen many students who attend the special centers and reassign some to special education classes on regular campuses, Tocco said. They also agreed to lengthen the school day at special centers, when necessary, to equal the county average for regular schools, he said. The improvements are expected to be completed by September.

About 840 of the most severely handicapped students countywide attend the centers, officials said. They suffer from retardation, autism and other mental disorders. Many also have physical handicaps.

Complaints from Downey parents and activists triggered the investigation, which began last year. Research has found that handicapped students who attend classes on regular campuses benefit by making friends and learning social skills from their non-handicapped peers.

More than 50 school districts throughout the county send their most severely handicapped students to classes run by the county Office of Education.

The county operates 10 special centers and runs classes on the regular school campuses of the districts it serves. The county serves about 8,000 handicapped students.

Last year, the Office for Civil Rights found that some county-run classes at regular school sites also were deficient. In some cases, handicapped students attended school for less time than non-handicapped students. Investigators also found that some extracurricular activities for handicapped students were inadequate and that speech therapy and other services were not always provided.

The Office for Civil Rights also has found that 31 school districts in the county violated the law by failing to ensure that their handicapped students received an adequate education from the county. The county Office of Education and the school districts could lose federal funding if the problems are not corrected.