I was picturing Shark Week when you mentioned the 'biting frenzy'! That sounds like a horrible situation and you must never be able to relax or take your eyes off those boys. That must be stressful all day every day. Not a good situation for anybody.

Have you discussed the problem with the parents and are they helping their boys learn that biting is completely off limits and inappropriate? That's when it's a dealbreaker for me, when the parents are not addressing the issue at home so that the children learn the rules are the rules no matter where they go.