crossma, you say you are considering moving your son to another primary school. I have to say in your position I might think that's the best answer. Much as I believe in negotiation and working with the school, from what you've said there are strong reasons to reject this course of action now. Or at least be prepared to.
From reading your posts I see you have tried to raise the issue with his teachers in the past 2 years? What about giving it your all, just the once more? but a time limit, see if there have been results, and if not then then move your son away.
You seem to have so much against you - no other parent will support you in this, the school don't follow an anti bullying policy and haven't taken you seriously to date, and, most importantly your son is having a miserable time in the playground. You sound at the end of your tether. Is a prolongued battle worth it?
I take it your son is at primary school so he's not following any exam syllabus. I am guessing but is he around 7-ish? if so, he'll have time to settle into a new primary school and he'll have a fresh start away from this bully and away from the damaging indifference of adults. Yes, in some ways it's admmitting defeat and yes it's difficult to move a child, but IME not impossible - my son has settled happily at three primary schools and I know plenty of other children who've happily moved primary schools too.
If you still want to fight this school you can continue to do that when your son is at another school. Keep your ear to the ground, be ready to pass on your knowledge to other parents of bullied children at the school.
I would only suggest this as a last resort - confront the school first, communicate with them, try to find a solution, but keep this as plan B.