Advice for my kid, please

Kim, sorry to hear about the crap your child has to go through. While it appears that the instructor is a grade-A asshole, it also seems he's an equal opportunity asshole in that he's rotten to everyone. Okay, iif he's that bad, then maybe the school can get rid of him if enough people complain. IDK what the laws are like over there.

As for your child, I have no words of advice to add to what everyone else has already said except to say "be strong" to your kiddo. If it comes to contacting a lawyer and suing the instructor and/or the school over mental cruelty which would mean outing your child, then maybe that's what you'll have to do. In the meantime, be the good parent that you are and offer all the support you can which you've been doing. All the best.