..and his teacher has told him to ignore it. 
I've been aware for a few weeks of some issues that my son is having with a child in his class, name calling, pushing, hitting all conveniently out of sight of an adult. Me and his dad have told him not to hit back and to tell his teacher, but the child doing the bullying cries to the teacher saying it's my son that's hit him.
I've spoken with his teacher and he says he'll speak to both boys and try to keep them separate, but I get the feeling he's sick of me going in, and I'm a nuisance.
My son came out of school last night in tears because he'd been in trouble with the teacher, for sticking up for himself, his bully had kicked him and punched him in the ribs and my son snapped and hit back, the bully has walked away again with no punishment, where my son has lost golden time. 
I know it must be very frustrating for the teacher, but no more frustrating and upsetting than it is for my son not being believed. He's such a sensitive and kind boy and he hates violence and confrontation. He's cried on the way to school this morning because he doesn't want to go, I feel so helpless.