Actually, the main bully is one who threatens to push my son off of the swings. The story has actually become more complex with additional bullying incidents that we hadn't known about before. We originally only knew that my son's food was being taken. It turns out that there were issues with multiple kids in different circumstances. The food issue hasn't happened again since the child involved was told to stop (I went to lunch and talked with the child myself and he seems to genuinely feel sorry because apparently he thought my son didn't mind). It doesn't seem like there is more to the food issue, although I can see why that would be a possibility.

I do have the principal's e-mail and I sent a message as soon I picked up my son, before even leaving the school. I think I will start documenting like Indigo suggested. The problem is that I'm not sure what I could ask them to do besides what they are already doing.