Keen interest in this. 2 children from DC class joined school after having been bullied at their old schools. Now, they have become bullies themselves. Unfortunately my DC has been their target this past year. We pulled DC and have switched schools. How do we keep DC from going down that path?
Are you sure they were removed from the previous school for being bullied? Perhaps that's just a line you were all spun and they were kicked out for being bullies there, too. I know people say that bullies are often victims of bullying themselves, In my experience many bullies have had massive chips on their shoulders about something, which they may have perceived to be victimisation or bullying, but wasn't.
The typical school bully usually has very different personality traits from the typical bullied victim.
When I was at school a lad from a couple of years changed school to the other one in the village-very usual. Dm saw them walking to school and said "Poor X, he had a hard time." I looked at him and said along the lines of "phew his form were glad he'd went, he was so mean to ..."
Dm looked at me and asked what I meant and I said I knew he was bullying a couple of children in the form quite badly, from both reputation and I'd seen it. His parents had been called in and told about this, and promptly withdrew him from the school and sent him to the other and told everyone he'd been bullied. Unsurprisingly he was a bully there too (knew people from brownies).