I appreciate all of the advice. It is difficult to say anything without it being apparent that someone provided information; I'd rather not have them know about the call, but it's hard to explain why I would be concerned without giving that away.
I've written down what my son says and what the caller said while I think about it. The caller said she had already reported what she saw to state authorities, although I don't know which ones.
This is a public school, but I'm coming to think that public school just won't work for my kids. When I was a child, I was horribly bullied by a teacher for my severe OCD. I remember it like yesterday; I am not willing to risk leaving my child in a situation where he is not respected and treated well.