Never had a bullying issue. However I can tell the story my Dad had as he used to be bullied for being skinny. The reason he was skinny was that he was ill, he was becoming a type 1 diabetic. He grew up in Scotland and every school he went to when he moved had the same amount of insulting and constant ganging up. It's not really ever bothered him as far as he tells me except for when his family moved to England and he came across the cocky guy in his year. The one that thinks he's king essentially... (I'm sure you've all had one in your years at school) He started a confrontation, pushing my Dad about for being Scottish and new. So of course by this point my Dad had enough of that and pushed him back, the bully then went to swing for my dad but he had already connected with the kid's nose, like a spontaneous reaction to seeing the bully start clenching his fist. Then of course scrambling on the floor as the nose break caused the kid to drop to the floor, my dad carried on pummeling the shit out of him - (a burst of built up anger after everything that happened before that).
Teachers broke it up and had to consider expelling him, which is funny as he'd only been there a day. But anyway as other kids came in to talk about what happened, turns out they were sympathetic to my Dad due to the way the kid had treated others (blinded another boy which was made out to be an "accident") & the way he'd been treated in the past. The bully got removed from the school, and wasn't seen around the area - apparently he got sent off to a boarding school or something to be straightened out.