I know that similar threads have been raised on this issue, where posters have suggested that the OP take it up with the school, but, without at all blaming my own child, I am looking for a different angle.
DS is a very gentle, academic type of child, who prefers the company of girls rather than boys, who mostly play football together. A new boy joined the school last year, who arrived with 'form' for negative behaviour towards other kids. Within weeks he'd mobilised other kids to kick another child who just happened to be passing by at play time. School took action and dealt with the matter very promptly.
The said boy now appears to moved on to my child. Lots of seemingly small things - hostile comments and malicious laughter, eg when DS fell over. I took a particular situation up with his teacher last term, who dealt with it very promptly. However, this boy seems to have started again and when he does, his mates join in with laughter. DS feels singled out. I know that school ran some anti-bullying sessions with the children last term, but clearly none of these kids got the point. Again, I have contacted teacher, who is very good.
I think we all know what makes a bully, but, without blaming either him or ourselves, I'm very afraid that my child makes a good 'victim': gentle, preferring the company of gentle girls, and not the least interested in football. So I'm afraid that, even if things can be turned around with the child who is bugging him right now, it seems likely that he will encounter other people like this in the future - school, college and workplace.
So I feel that even changing school won't completely solve this for my child. What can I do to help him? I've tried telling him that this boy is unimportant to him and that he should stay close to his friends, but I know he can't always be with them. For the record, we have tried martial arts, but DS felt it wasn't for him.