I have been down this road and it can be frustrating. Make sure the Principle knows, there should be action on his/her part. You said the teacher was getting on these kids but that may not be enough. I had to resort to getting a little nasty with the parents/school telling them it would stop or I would be seeking legal advice. There should be zero tolerance to this kind of behavior. They wanted to have my daughter change classes but she liked her teacher. I told the Principle that my daughter is not going to be punished by loosing a favorite teacher and told them to remove the kids that would not behave to another class. The parents of the bullying kids were just as bad. One ended up being expelled and had to go too another school which was a big hassle for the parents. But they did nothing so they suffered the consequences. My daughter did not want to go to school and became depressed. I was very worried about her. I did not want to be one of those statistics were my child took extreme measure to escape the bullying.

I know this can be a tough situation to be in. Children have enough stress they do not need to be hounded at school. Being in 3rd grade can be tough but it doesn't get any easier. One thought though, traditionally taught Karate may be good for her. A dojo/studio that teaches the philosophy of martial arts, not just the moves.

Good Luck