Teacher increased anxiety in my son due to screaming

I wanted to reach out here to parents to see if anyone has experienced anything like this. My 8 year old son (level 2 autistic) goes to a private school and last year (2nd grade ) he had a teacher that was extremely strict, high strung and yelled a lot. My son has had a RBT in there with him the whole time and kept me informed of what was going on. The first instance of her yelling at my son directly to answer a math question she put so much pressure on him to answer it and he shut down. I went to the principle and moved him to another classroom. The second time, she was found screaming at him in the hallway in front of the other class he was moved to that he needed to get to the library because he still had electives with her class. So fast forward to summer. His anxiety is so much worse (he’s had chronic stomach aches daily for years due to food allergies and anxiety ) it’s so bad that he hates his summer program at school and tells me he’s afraid people will yell at him. I’m upset because I’ve already been trying to figure out how to get his anxiety under control and this has made it worse. What do you all do about anxiety and since I consider this a trauma for him, what do you think would help him move on and like school again? He’s becoming withdrawn more from the outside world and not wanting to go to places like trampoline parks or things he used to do. I’m not solely blaming that on this situation but I don’t know. Maybe he’s just changing a lot at 8. I’m very upset and realize I can’t protect my son from everything in life like I’d like to. Especially a person that was well aware of his issues and couldn’t keep herself controlled in a classroom setting. She has since resigned. Thank God.