I am sorry to hear that your child is experiencing this. It must be really horrible. As with any conflict a child may come up against in life,it is particularly hard when having to deal with it at school,because you have no choice,they have to go to school. My son who will be going to senior independent school in Sep, is small for his age,he also had perthes desease,which has left him with a slight limp,more apparent when he runs. This last year and a half has been difficult for him. Apart from the obvious name calling,he has been kicked,punched and winged at by the same looser for almost all of year 6..This looser will take his problems to their next school as the parents have not addressed his problems(since year 1)..I educated my son,not just about the academic side of life,but also about the real life issues. Life is hard, and we must teach them this. No matter how much you try to protect them. I have been down the education road,lost my rag with the parents,screamed at the teacher. There is only so much you can do,i am afraid. As parents,we have been there,seen it, done it,and WE are still here! Our children have to learn that there are not very nice people out there,and although most people are nice,they will always have to face some kind of conflict...It is inevitable.
Your child has had the best start in life,he has you,a loving parent. He WILL survive.