Although I'm not a parent, so I'll probably get shouted at for not being in a position to talk, but I disagree completely with homeschooling in general, except for certain cases where the child really cannot get along at school, for example autism or other such conditions.
Obviously staying at a school where he is persistently bullied isn't an option that you could put him through, but from a social point of view, surely he needs to be at A school, even if it isn't a top private school? Are there no other schools he can try, after all you can take him out of school to stop the bullying there but if he doesn't establish social skills among his peers at this age then he won't find it any easier when he has to get a job-however clever he is-and that's not really a situation you would be able to 'take him out of' then.
Sorry if this comes across as a bit harsh, I'm just trying to see it from a different perspective.