Heather Kline was skipping classes to spend time with Troy Mansfield, a popular football coach who'd first targeted her when she was in his third-grade class. He gave her gifts and rides in his car. She sat on his lap. The bond ran so deep that the student got chastised repeatedly — even suspended once for being late and absent so often. But there were no questions for the teacher, until the girl's mother got suspicious.

"I didn't have my childhood," says Kline, who's now 18 and hoping to get her GED so she can go to nursing school. "He had me so matured at so young. I remember going from little baby dolls to just being an adult."

Heather read Mansfield's e-mails and instant messages aloud at his 2004 criminal trial, from declarations of true love to explicit references to past sex. He's serving up to 31 years in state prison.

Elsewhere, there have been fitful steps toward catching errant teachers.

More states now require background checks on teachers, fingerprinting and mandatory reporting of abuse, though there is still a lack of coordination among districts and states.

U.S. Supreme Court rulings in the past 20 years on civil rights and sex discrimination have opened schools up to potentially huge financial punishments for abuses, driving some schools to act.

And the National Association of State Directors of Teacher Education and Certification keeps a list of educators who've been punished for any reason, but only shares the names among state agencies.

Another problem: Because teachers are often allowed to resign without losing their credentials, many never show up on the list.

"They might deal with it internally, suspending the person or having the person move on. So their license is never investigated," says Charol Shakeshaft, a leading expert in educator sex abuse who heads the educational leadership department at Virginia Commonwealth University.

It's a dynamic so common it has its own nicknames — "passing the trash" or the "mobile molester."

Aaron M. Brevik is one educator who fell through the cracks.

An elementary teacher in Warren, Mich., he was accused of using a camera hidden in a gym bag to secretly film boys in locker rooms and showers. He also faced charges that he recorded himself molesting a boy while the child slept.

Found guilty of criminal sexual conduct, Brevik is now serving a five- to 20-year prison sentence.

What Michigan officials apparently didn't know when they hired him was that Brevik's teaching license in Minnesota had been permanently suspended in 2001 after he allegedly invited two male minors to stay with him in a hotel room when he was a principal in southeastern Minnesota.

"I tell you what, they never go away," says Steve Janosko, a prosecutor in Ocean County, N.J., who's handled educator abuse cases. "They just blend a little better."

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Contributing: John Parsons, special projects manager for the AP's News Research Center