War with a Two Year Old

I'm at war with a two year old and I don't mean Anna. There is a little boy in her class that is a bully. She has been bitten twice in the last two weeks and he pushed her down in front of me yesterday afternoon. I witnessed him picking on her once at a school party last year. I know it's hard for me to say anything since Anna went through a biting stage for a month or so, but she was only 15 months old at the time. This little boy is about 27 months old. I think he should now better by now.