I had a daughter who had this same problem in 2nd grade. She actually was in a full time Kindergarten and we moved here and she loved school. I did not recognize the signs and I tried my best to help at home. I had a medically challenging baby born the March before this, so I was rarely around as I spent most of my time and energy on the baby. I counted her problems on the instability of home life. It wasn't until late in the year (and not worth the effort) before (in talking with a friend that worked in the school) I realized that the teacher and some of the kids in the class even were adding to the problem. I know I couldn't do anything at that point, but I made a point to make sure she was not in the same class as these bullies and made a point to get a good teacher this year.
It isn't the fault of your child nor the teacher. But we all have our own personalities and at a young age, you should not be forcing your child to get along with someone that clashes with their personality. So as those before me have suggested, observe the class and possibly talk to different aids that might come and go. The teacher and students will behave for a one time observance. So if you can't get involved, talk to other mom's and get their opinion.
Good luck