Bully

So, Jax has a bully in his class.  I didn't think we would have to deal with this stuff until much later in life but what can you do.  A couple of months ago, I brought him to school and they were coloring on the table.  The teacher made a space for Jax and gave him a crayon, he started chewing on it and within a minute, this little girl comes over and takes it out of his mouth and starts coloring with it right next to him.  He looked shocked and started to cry.  The teacher and I both saw this and I picked him up and moved him to another part of the table and gave him a new crayon and he was fine.  A month ago, Tony dropped him off at school and he had his pacifier in his mouth.  As soon as he put Jax on the ground, the little girl came over and took the pacifier out of his mouth and put it in hers.  Jax, of course started to cry.  Then, a few weeks ago, Jax started biting and hitting out of nowhere. Not a lot, but enough that we noticed.  He had never done this before, so we figured he must be learning it from someone at school.   I talked to the teacher about it and asked if anyone was hitting or biting and she said that yes there is a problem arising from one of the kids and the others are just copying the behavior. They have been trying to correct it. She said she had only seen Jax do it twice and both times he stopped when they corrected him.  And he only did it to the kid who had hit or bit him.  I'm assuming this is the same little girl who has given him problems before.  She is a cute kid but she is big and brutish.  On one hand, I know he shouldn't hit or bite back, but on the other hand, I'm glad he is standing up for himself and put her in her place.  Is that bad of me?