All part of life's rich tapestry, I am afraid. As a parent, I have been there myself and know how you feel. But bear in mind. Teachers are all different and as he progresses through the school and then secondary school there will all sorts of different personalities to contend with. If he had a sweet quiet teacher before, this one might seem dreadful, to the children concerned but please think before making any complaints.
My child's teacher from age 7 to 11 shouted her head off and all the kids used to be terrified of going into her class. It turned out that she was the teacher that he and the others think back to with the most fondness. She was a great teacher with years of experience and taught them a great deal both academically and about that big wide world out there. They didn't even take any notice of the shouting after a few months - they knew her bark was far worse than her bite. Children quickly learn these things.
It is just an opinion, but see how it goes with your son. He has to learn to cope with all sorts and you can't be there to protect him.
By the way, being of senior years, I can remember teachers throwing things like board rubbers at us. Not that I think this was right, far from it, but we coped and learned to dodge the rubber and still managed to enjoy school and not live in fear.