Have you taken this matter to the school board? If you have and you are not getting the proper help, then may I suggest talking to someone that works at your local paper. Try to find someone who is willing to write a story about it and make it public. Give out the schools name, principal's name, the bullies family name and the names of people in the school board. Tell everyone in your town what is happening to your son. I believe you will see some action taken once these people see their names in the paper. This is very bad for school buisness. You do not have to slam the principal, but when people around town realize he is one of the people who let violence happen right under his nose and turns a blind eye to it....he will see the need to get something done.
Another suggestion, if you do not work, I say make suprise visits to the school. Pop into his classroom and make your presence known. Pop into the principals office unannounced. Keep them on their toes. If you have a day to kill just go sit in your sons classroom and observe how things are running.
You might also want to consider home schooling your son next year. Your local school board office can help you get that started and they will provide you with all the teaching materials that you need free of charge. If your son is this stressed out by going to class daily then home schooling is probably your best choice. Your son is just too young to have to be this worried for his safety. This bully is going to leave very deep emotional scars if your son is not removed from the situation.
This school year is almost over. I say you go to school with your son everyday. Sit in his classroom. Don't give that bully another chance to terrorize your son again. It may not frighten the bully , But you are giving your son the needed reassurance that he needs to feel safe.
I don't know if any of this will help you. I do hope something I have said can be usefull for you. I feel for you and your son deeply. I remember going through these issues with my child too. I have since started home schooling and believe me it has made a world of difference for all of us. I now have straight A students and they do not get bullied for it. Please keep in touch.
Mickie