Until yesterday, I only ever found out what happened in my son’s sex-ed classes by asking him about it. That was painful enough. In elementary school, he apparently learned that HIV is hereditary because you get it from your mother. In middle school, he had to help the teacher explain something about sex anatomy when the teacher was stumped and my son happened to know the facts. (I am a sex researcher and I work on intersex; he knows a lot about sex anatomy.) Now he’s a freshman in high school, and his sex ed is being taught in a health class by a gym teacher in conjunction with some “special helpers.” Two evenings ago, as we were driving back from the vet with a pet rat suffering from a bad foot, my son broke it to me: They are teaching sexual abstinence in the class. It’s not abstinence only, but it may as well be…