Wow Lepa. That sounds like a great school and what a relief to have such a positive experience. It does sound like that are getting to the math component and perhaps once they really get to know your son they can put a more comprehensive plan in place for him. I agree with others that there is nothing wrong with having a conversation with the school saying pretty much what you have said here. Tell them about the great things you son is doing and thank them. Then mention the math and ask if they have any ideas.
The other thing I would do is look for a math mentor for him. Someone he can hive his discussions with and keep him enthused. I am not necessarily thinking formal tutoring but a tutor who would work as a mentor. It should be about fun and keeping him sparking with those great thoughts.
Congratulations on finding such a great situation for your son and for always looking for ways to make his life better.
