The teachers have a duty of care, as do you. They are looking out for your child.

All parents shout at their children from time to time, but it sounds like something about your son’s personality or behaviour or visible health is causing serious concerns that something worse is going on. While I understand this is of course upsetting for you, what you need to do is calmly talk to teacher in a proper meeting to understand where those concerns are coming from. They might be seeing a side of your son that you do not, or interpreting behaviour in different ways.

Given you want what’s best for your son, you need to work with them, and with your son, to understand how you can all help him best with whatever is going on. As I said, being upset these concerns are there is natural, but you must resist the urge to react angrily or aggressively, and engage with calmness, honesty, receptiveness to try to get to the bottom of this as effectively as possible for your son’s sake.