I'm sorry to hear about your husband and the new principal -- is there a teachers' union down there that hes a member of? Maybe he could talk to them?

I'm not sure how the school system in the US works. Is it possible for him to look into a new school after the term is over or would he lose senority/tenure? It might be a good idea for his sanity if nothing else, since butting heads with your boss makes for a terrible workplace