Somebody mentioned in the comments to file a complaint and talk to administration. 100% do this. I had teachers like this in the late 80’s/early 90’s do this, which I can dismiss as just not knowing any better, but in 2021, this is completely unacceptable. People need to be educated and taught that stuttering is a real disability that is an every day struggle. Teachers need to know this more than anyone. If you don’t stand up to this it will eat you up inside. I still think about people I let slide in my youth that still makes me sick when I think about it. HOLD THAT TEACHER ACCOUNTABLE. You’ll love yourself for it afterwards.