I really hate to say it, but back in the ‘bad old days’ of the 60s and 70s, when I was at school, the problem would have been solved in short order, and in the same way bullying was often solved. At some point the violent child would have picked on a kid who was bigger, tougher and meaner than them, and would have got a pasting. It was amazing how that experience suddenly put an end to ‘impulse control problems’, in the same way that the cane was so often effective in curing ADHD.
Such afflictions are explanations for bad behaviour, certainly. But it does not follow that they should be made excuses for it. Also, children no longer learn to stand up for themselves, but are taught to run to authority figures such as teachers, who are often impotent to offer any real solution. The standard response to complaints of bullying by the parents and teachers of my era was “Well, next time he/she hits you, hit them back, harder!”. I can’t answer for other people, but in later years I was able to quell office bullies with a look, because I’d been taught that my safety and comfort was my responsibility, no-one elses’