My son was in class with a difficult teacher at the beginning of his K year. She would gripe at one little boy for being too tall, tell the children they could not sit certain ways on the floor, expected all to quietly sit and color to begin their day.
Much of her approach was very lazy teaching. My child had been an exemplary student the previous year (also full day at same school) and had never had issues at school. There was a traumatic event unrelated to this teacher that made things worse but he mostly had her all day and she was very cool with all the children. She clearly did not like my son and he knew it.
My child also had undiagnosed challenges that significantly affected his ability to perform in her "all overheads and worksheets" teaching method. However, not understanding all the impacts, my husband and I continued to try to help him work through it. School refused to move him to another teacher despite very significant reasons to do so and her unwillingness to give any effort at resolution. Mind you this is a pricey private school.
Our result was a painfully affected child who has been riddled with anxiety and began pulling his hair out literally. (Later diagnosed with Anxiety Disorder w/ elements of PTSD.) We did pull him out at this point realizing how bad it had become. I regret everyday he was in her class. She was too tired of teaching to be effective and she clearly disliked many of her students.
When he got in to a better school situation his hair grew back. His nightmares began to go away and we saw him begin to go back to who he had been before. It was much worse than we ever knew in that classroom and I would urge you to listen to your child. You know him. You've seen some very bad things happening. If his teacher acts this way when she knows parents are watching, what do you think she would say and do when parents aren't around to witness it?
So sorry you have found yourself in such a situation... Is there a possibility of homeschool and return the following year to this school if you desire?
