Plenty? I've almost never seen it. I had a few teachers drop occasional insults toward me but they would never dare do anything to me like a kid would. They can't even spank students anymore. Almost every issue that a kid has with a teacher is caused by bad behavior. Of course I haven't been in grade school in decades and I went to probably a nice school in the scheme of things. I have seen quite a few stories of teachers doing awful things to their students, for example harassing them about politics. But I really think these cases are rare, and most likely kinds of teacher harassment are easily avoided by students.