Could you mention that he seems to have voraciously consumed most of the second grade curriculum already? I asked the school to administer an end of grade assessment(They told me they didn't have anything like that which is untrue and not the point here).

If they agree, let them do it and then ask what they suggest? Add your suggestions to theirs and see if you can work something out.

Your school sounds like they have been open and flexible so far havent' they?