I'd caution you against tying compliant behavior in class to rewards at home. Obviously the situation at school is a bad one for him, one in which he has every reason to be acting out, and what's more, I'm sure he's aware that you don't think much more of this teacher than he does. If you disapprove of his teacher (whether you actually voice your disapproval or not makes little difference), that can easily be taken as giving him permission to act out. Regardless, punishing him at home because he doesn't follow the instructions of someone he knows you don't respect is confusing at best. When a child has a bad situation at school, home should be a place to, as EastnWest says, "decompress", with whatever resources are available. He should be allowed to be as happy as you can possibly make him in those post-school hours.
As for the next four weeks, I'd say get him out of there. "Just quit when things are tough" is indeed a bad lesson for him to learn, but so are "keep banging your head against a brick wall no matter how much it hurts", "do the same thing over and over again expecting different results", and "if the normal path doesn't fit you, keep at it anyway and don't look for a better alternative".
