Just that.
He's come home a couple of times crying because other kids have been saying "your mum is a shit" and other delights.
He can be wild and annoys the other kids but he's sensitive under it all and he's really upset. The other kids to be frank are not that nice; they've encouraged other younger kids to throw mud at him, they've thrown his stuff in the ditch and he's come home with torn trousers and nasty bruises. Mind you he's no angel either, but I dont think he'd go anywhere near this far ... he notably tends to get more beaten up than be a beater-upper.
The main thing is that I'm just not sure how to handle it other than lots of hugs and saying "look, this is them calling names, it isn't to do with either you or me personally". He's starting to be afraid to play outside. He really can't stand it if people attack his mum or his things.
We are moving in a year's time but until then any hints on what to say to him would be appreciated. I did manage to speak to one boy's mum and got an indifferent apology, but it's happened again and I'm short of ideas on how to reassure and help him handle it.