I would have to say, that once all resources are exhausted and you can no longer work with the school, then it's time to walk. Granted, it has the art aspect, however, is there a way you can still pull it off by having private classes, or having your son mentor a respected artists etc? It doesn't have to come from the school. If you can easily walk away from the the school, I would guess that the only reason you are staying is the art. Defenitely request that your DC is not placed with the other child and try to resolve things with the school. if the school isn't willing to help much, then it's time to move on.
