Nine months ago, Isabel Rosendorf was desperate for a center where her daughter Diane, severely mentally retarded, 21, and no longer eligible for public education because of her age, could spend her days in classes and therapy.

Rosendorf, a clerk-typist at Montgomery College, took six months' leave from her job to begin the search for the right place. Now she has extended that leave an additional five months and says that she still hasn't found the right place for Diane, although the Maryland governor's office, the Montgomery County school system and the state Mental Retardation and Developmental Disabilities Administration have looked into the problem.

"The care of my child is my priority," said Rosendorf, who has refused offers to place Diane in care centers for the handicapped. What Rosendorf wants is to have her child continue to take classes at Longview Center, one of three Montgomery County public schools for the mentally retarded. Officials from the school district say this is not possible because Diane has reached the age of 21, the age when funds to provide education for the handicapped are cut off.

Officials in the Montgomery school system acknowledged last week that Rosendorf's case was "a problem," but said it is not one that should be handled by the school system.

"I don't believe the school system should be taking care of a child forever," said Hiawatha Fountain, associate superintendent for special and alternative education. "What Mrs. Rosendorf is asking for is something that needs to be done by a different agency."

Federal law mandates that developmentally disadvantaged children under the age of 21 receive publicly funded education. After that age, the mentally retarded can participate in programs, if they are available, through community-based agencies. The school system has no obligation to provide services.

If the school system continued to provide education for Diane Rosendorf, it "would have to do it for anyone over the age of 21 who wants to stay in the school system," said Lois Meszaros, director of Maryland's Mental Retardation and Developmental Disabilities Administration, the agency that funds community programs that provide day and residential programs for the mentally retarded.

Meszaros said the state will provide funding for Diane's therapy and that Rosendorf has been offered programming at Centers for the Handicapped and custodial care at the Vocational Training Center for Severe and Profound Retarded operated by the Montgomery County Association for Retarded Citizens.

Rosendorf said she has not been offered space in the Centers for the Handicapped, a vocational training program, and that she refused care for her daughter at the MCARC center because "they just let them sit there."

"Why can't [the schools] make an exception for Diane? All I want is for them to provide therapy. I'm not asking for taxpayers to pay for institutionalization. I keep Diane at home; all I want is for them to provide therapy, which costs the state far less than institutionalization," Rosendorf said.