When I was in the third grade in suburban Massachusetts, I was bored in class. Somehow it was arranged that an MIT student (can't remember if grad or undergrad) would come chat with me periodically, I think for an hour or two a week. This was wonderful and he suggested all sorts of books and suchlike and explained what a derivative was.

I gather you're in the Pioneer valley. You might see if any of the college students around would like to spend time interacting with your young'n.