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What's Behind Teacher-Student Sex?

Several cases involving alleged or proven sex between female teachers and male students have been hitting front pages across the nation.

It all seemed to begin with Mary Kay Letourneau. The Seattle teacher served seven years in prison for molesting a sixth-grade student. That relationship eventually produced two children. Letourneau and the now 22-year-old were recently married.

Unlike Letourneau, Pamela Turner, a Tennessee gym teacher, pleaded no contest to having sex with a 13-year-old student and is serving a nine-month sentence that resulted from a plea deal.

Sandra "Beth" Geisel, a former New York Catholic high school English teacher out on bail on statutory rape charges involving a 16-year-old student, was arrested Friday for alleged drunk driving. The Albany-area mother of four is the wife of a bank president.

And in Florida, middle school teacher Debra Lafave, has offered an insanity plea for her alleged affair with a 14-year-old boy.

What's behind the seeming spate of teacher-student sex?

Lafave's ex-husband, Owen Lafave,

with co-anchor Julie Chen on The Early Show Monday, along with Dr. Julia Hislop, a clinical psychologist and author of the book "Female Sex Offenders."

Lafave says his ex-wife has never told him why she (allegedly) did it "and that's one of the hardest things that I've had to go through, is that I've never received a reason why."

He says he had "no idea" anything was going on "and hindsight is 20-20. I can look back now and see some things that were peculiar about her behavior. But I had no idea anything like this was going on."