What does school do about the biting other than send him home? They should have a behaviour policy to use to control it. Ask to see it and go through it with him and his teacher so he fully understands it.
My answer to him being continuously sent home would be to refuse to collect him until the end of the school day. I might even go so far as to switch my phone off. If his behaviour is extreme enough for them to be regularly sending him home they should pointing you in the direction of support.
