Dear Prudence: Three years ago, I divorced after only 18 months of marriage.

My husband was a university professor, and he had been having a nonsexual but emotionally intimate relationship with a student. I wanted to repair our marriage, he did not, and we divorced.

During the divorce, many details of similar "extracurricular activities" came to light. He was fired from one high school position for having an inappropriate relationship with at least one female student. After our divorce, I discovered that he had a sexual relationship with another student at his university, and that he had been urged to resign. He moved away with this former student, and we are not in touch.

Recently, I discovered that he is teaching at a prestigious co-ed boarding school and lives at the school. What is my responsibility in this situation? Aside from my bout of curiosity, I have moved on and have a happy life post-divorce. I assume a prestigious school does a background and reference check, and that they didn't find anything unsatisfactory.

Still, there is a part of me that thinks — what if they don't know? I feel like Eve — I ate from the tree of knowledge, and really wish I hadn't.

Prudence says: It's likely that the school that hired your ex-husband did do some sort of background check but found nothing alarming. Your sleazy ex appears savvy enough not to get into bed with students until they are no longer minors. So when his current employer searched for a criminal record, they didn't find one. To avoid lawsuits, most employment references simply confirm that someone worked there on a given set of dates. And since your ex was allowed to resign from his university post, all he had to do to explain his departure was to say he realized his heart lay with high school students (for sure!). I think the school needs to know. But while you've collected an alarming pattern of stories, your documentation is almost nonexistent. Were you to be identified as the source of this information, you could face a defamation suit. So I say it's time to write the good old anonymous letter, and arrange to send it from a state other than the one where you reside. Enumerate the facts you've related here and stick to them, and state your concern about someone with this personal history being in the teaching profession. Send it to the head of school and the officers of the board of trustees. Let's hope it puts a crimp in their summer vacations and forces them to take quick action. But be aware that, unless your ex gets nabbed by the criminal justice system, there is likely another teaching position in his future.