Agree with all the above. A teacher calling a little kid ANNOYING. That is just uncalled for.

First month of Kindergarten. Lots happen. Seems all the kids are testing each other, pushing the boundaries. That being said, kids calling each other "stupid" etc is unacceptable and should be addressed.

My DS4 is in his 4th week of K. The first week didn't start out too well. There was this kid there that ended up hitting DS in the head. When I asked DS what he had done he said very clamly that "I grabbed his arm and told him that I am strong enough to rip your arm off and I don't want to have to do that".
OK, a bit of a questionable response but at least the boy didn't do it again. Come to find out that he is now playing with DS. I think the whole thing was about wanting to be DS's friend and he was doing it to get his attention.

Do they have a chart at your son's school? They have a tree at DS's school where you can end up in the "ready to learn" range or "make better decisions" range. Seems they are VERY strict about this and will call the parents if a kid completely falls off the chart. I like this approach. Keeps the kids on track.