Sexual offenders are finding jobs in American schools, sometimes carrying with them glowing letters of recommendation from officials who knew of inappropriate behavior.

A Government Accountability Office report that was requested to explore the problem and was released Thursday examines in depth 15 case studies at public and private schools that employed such individuals.

In eleven cases, GAO investigators found, the teachers or staff members had targeted children before, and in six of the cases they were in new positions where they abused children again.

The GAO report follows a 2004 Department of Education report estimating that millions of students experience sexual misconduct by a school employee at some point between kindergarten and 12th grade.

Persistent achievement gap vexes education reformers: Six takeaways

There is no federal law regulating the employment of sex offenders in schools, and state laws vary widely, the GAO notes in its report. But often school officials are ignorant about those laws and policies that do exist to prevent schools either from hiring sexual offenders or from issuing them recommendations.

“There are still school districts that don’t want the publicity of having a person like that in their district ... and have no ethical qualms about putting him or her in charge of children in other places,” says Robert Shoop, director of the Cargill Center for Ethical Leadership at Kansas State University and a forensic witness in cases of school misconduct.

Without mandated training for educators, and punishments for those that pass along the offenders or fail to check backgrounds thoroughly in hiring, “I’m not incredibly optimistic that dramatic change is going to occur,” Mr. Shoop says.

The GAO case studies revealed four key factors that contribute to the continued presence of sexual offenders in schools:

• School officials allowing teachers to resign rather than be disciplined for misconduct with students. In Ohio, a teacher was “having relationships with students that were ‘too much like boyfriend and girlfriend,’ ” the report notes. Officials felt they didn’t have enough evidence to fire him, and he received a letter of recommendation from the district. The teacher then taught in another Ohio district and was convicted for committing sexual battery on a sixth-grade girl there. Similar circumstances were found in 3 of the other case studies.

• Schools not performing criminal history screenings. For example, a man was allowed to volunteer as a coach at a public school in Florida without the background check required by school policy. He had been previously convicted of having sex with an underage boy, and was later arrested for sexual contact with a student athlete. This was a factor in 10 of the case studies.

• Schools that do perform checks failing to be thorough enough or to do them on a recurring basis after hiring people. Schools can request the Department of Justice to conduct fingerprint-based checks of employees who work with children, but law does not require schools to use the service. Only a few states require recurring checks.

• Schools failing to ask about red flags on applications. An Arizona school, for instance, did not follow up on an applicant who answered yes when asked if he had been convicted of “a dangerous crime against children.” He was later arrested for abusing a young girl at the school.

“Our schools have a fundamental obligation to children and parents that all students are safe at school. What we see here is a major violation of that trust,” said Rep. George Miller (D) of California, chairman of the House Education and Labor Committee, in a statement releasing the report.

Mr. Miller, who requested the GAO investigation, has pledged to work with Republican counterparts to develop related legislation.

But even if such legislation goes forward, it may not have much impact unless it comes with dollars attached, Shoop says. “So much legislation is enacted but there is no enabling legislation that funds it, so it becomes a burden on the school district.”

Persistent achievement gap vexes education reformers: Six takeaways