Having been in a similar position with DS (ADHD) what should be happening, and what you have to accept and be the bigger person, are two different things.
DS was at a private school. Class/year was abnormally small, (6 children) so everything he did was more noticed and gossiped about. The other children were actually really nasty to him. Goaded him (who doesn't love to wind up the guaranteed reactive child then cry victim
) but there were plenty of incidents where he was just poorly behaved independently. It was like he was some kind of self fulfilling prophecy, labelled as the naughty kid, so that's who he was. And the school should have done this, that and the other regarding senco, in school support, parental meetings, and failed to deliver.
The deputy was an old school, up his own arse, "discipline the ADHD out" git. Declared "we don't have badly behaved children at this school". Who was also far too close to a mother, whose child was in DS' class. She complained continually that she wasn't paying fees to have child "like that" there. They didn't have a proper senco and she somehow got appointed "acting senco". I say somehow, it was quite clear why. The deputy, and her, rallied round to recruit others for support in their "get rid of him" campaign, and DS just got ostracized.
The head was newly appointed and actually a lovely guy. But lacking in backbone and didn't want to stand up to the deputy (who'd been there for years and acted very much like it was his school, everyone seemed intimidated by him). We had a meeting, and he said, I know they're going to instigate so many complaints I'll be forced to show action. They won't stop until he's excluded. That's when they'll be happy.
I thought about it, and agreed, I couldn't be arsed to fight them every day for the next two years. It would be better if I removed him, by "choice" than to have permanently excluded on his record. So I did. The head even said, off the record, if it was my son, I'd take him out. Quite the admission of his own school.
Is it right, or fair? No. Do I want my son treated like that by arsehole adults and their carbon copy children 5 days a week, and pay for the privilege? Also no. So I picked my battles. He's now in a great school.
So, my advice. The school sounds shit and unsupportive. Do you think they'll suddenly become fantastic? So why the battle to keep him there, when they'll always be looking for a way to be shot of him. It will just be miserable.
The only thing I'd have done differently, is report DS old school, as now, seeing how things should be done, I realise just how appalling they were. So take the boy out. Then throw the fucking book, as publicly as you can, involving governors, report to the board of education, inform your local MP.