Thousands of American parents are turning their children over to social workers or the police because it is the only way for the children to receive treatment for mental illnesses, a national report concluded yesterday.

More than 12,700 children were placed in the child welfare or criminal justice systems in 2001, the General Accounting Office said in the first attempt by the federal government to assess the scope of the problem.

And that number may be a small fraction of the actual total: The GAO report said 32 states, including the largest five, did not provide data on how many children with mental illness were sent to child welfare agencies to receive treatment, largely because the information did not exist. Data on the number who ended up in the criminal justice system were based on just 30 counties nationwide. Neither the states nor the federal government has systematic data about the extent of the problem.

As a result, smaller states and counties accounted for the largest numbers in the report. Minnesota reported 1,071 cases of children being placed with child welfare services to get treatment. Although Pima County in Arizona said 1,750 children had been placed in its juvenile justice system for this reason, Philadelphia counted 500. Los Angeles provided no estimate.

Parents took these drastic steps because they were unable to cope with their mentally ill children or because of the cost of care, insurance problems or lack of access to services, the report said. Outpatient treatment can run as much as $100 a day, and residential inpatient care can exceed $250,000 a year. But many private insurance companies do not offer coverage for mental illnesses that is comparable to that for physical ailments -- an imbalance that President Bush and some in Congress have vowed to end.

"This is a real tragedy," said David Fassler, a child and adolescent psychiatrist in Burlington, Vt. "Families should never have to give up custody of a child in order to receive critical mental health services. As a society, we are letting our kids down."

The problem apparently affects families from a range of financial backgrounds, and adolescent boys were the ones most frequently turned over to social workers or the police, largely because they "exhibited behavior that threatened their safety and the safety of others."

Fassler said adolescent boys with mental illnesses are more likely to "act out," and adolescent girls with similar conditions tended to "act in" and become withdrawn. Appropriate evaluation and treatment, he said, could control the risk of such violent behavior in children with mental illness.

The GAO said families with mentally ill children reached the crisis point through a variety of circumstances: One Kansas family reported that three children in the home had refused to live with their brother, who has bipolar disorder, or manic depression, because he "is very aggressive, and has molested other children in the past."

An Arkansas woman reported having to quit her job because she had to care full-time for a sick grandchild.

And a Maryland family with a child who was both developmentally disabled and mentally ill found that facilities for developmentally disabled children turned the boy away because of his mental illness, while facilities that served the mentally ill rejected him because of his disability.

"There are services in short supply, and there are difficulties in eligibility for different programs," said Diana Pietrowiak, one of the authors of the GAO report. "For example, Medicaid officials in three states said some children lose eligibility because their family's income increased beyond the threshold," and families can't afford the care on their own.

Sometimes, she added, mentally ill children are shunted in and out of treatment as the family's income fluctuates and the children acquire and lose eligibility for Medicaid coverage.

Budget crunches in states are almost certainly making the problem worse. The report noted that New Jersey has limited the number of children who need the highest level of care to 180 a year. But juvenile justice officials in the state estimate that at least 500 children under their supervision need such care.

There is also a chronic shortage of highly trained child psychiatrists as a result of low rates of reimbursement and insurance coverage, said Rep. Patrick J. Kennedy (D-R.I.), one of the members of Congress who asked the GAO to conduct the study.

Kennedy, Fassler and others said that more efficient use of existing resources, such as matching children with less critical needs with less expensive providers, could help keep families out of crisis. So could better prevention efforts.

"Most of our mental health system is based on the crisis management model," Kennedy said. "The real challenge in bringing the costs down and to be more effective is to do more prevention and early intervention as well as more community-based support services."

The GAO report found that communities that were able to lower the incidence of mental illness and keep troubled children and families intact were those that focused on prevention and flexibility.

In Shawnee County in Kansas, the Children, Youth and Families Resource Center offers psychological, medical and emotional services under one roof. A program called "Success by Six" helps children before they reach school age. Social workers visit newborns in hospitals, screen families at risk and conduct home visits.

"Getting rid of turf battles and [the feeling of] we're all in this together leads to a different organization," said Brenda Mills, chief executive of the center. Still, she said, coming budget cuts may hurt prevention programs. "Dollars are getting squeezed, and they are pulling dollars away from things that are working."