[Buddy-licious]

First of all, I am so sorry that your little boy is upset and I hope you can get to the bottom of this issue.
I do think that teachers have the hardest job in the world. I definitely would not want their job!!! I volunteer at my son's school alot and I see that all the teachers have a huge problem with disciplining children. There are so many rules and guidelines that teachers have to follow regarding disciplining children but I can assure you that yelling at your child is not one one them. However, I have seen the writing of names on the board used a lot....or some teachers have a system of "pulling a card" (cards have each childs name on it )....the goal each day is to not have your name on the board OR to not have to "pull a card". The first question I ask my son each day after school, "did you have to pull a card today?" No cards pulled means that he behaved well that day.
Perhaps you should discuss with your childs teacher her discipline rules then review those with your child. Obviuosly, yelling is not something that he is use to and this has upset him. Perhaps you could explain this to his teacher. No yelling!!!
I would definitely start with speaking with his teacher first. Hopefully, you can resolve the problem with her before going to the principal. This is a very delicate issue because I would not want to piss the teacher off ....in the past when I had a disagreement with my sons teacher ....I was afriad that his teacher was going to take it out on him.
I bet if you tell your son's teacher that he is crying each night because he is scared of her.....I bet she will be feel really badly. Or at least she should feel bad!!!
I hope you get to the bottom of this. Most of all, I hope your little boy is no longer scared. Keep us posted!!!!