Thanks for the great suggestions so far. Keep 'em coming.

I'm not sure I have him figured out mathwise. He seemed not so mathy up till about 6 months ago. He hasn't expressed the same natural interest in it that DD did at his age; he just picks it up super fast, if taught. I think he's picked up a lot from playing dice and card games for older children.

The good news is that he will presumably test into DD's gifted magnet and start there in grade 2, so we just have to keep him...not miserable...till then. (The magnet is likely not totally sufficient for a kid who is more than MG, but it's been "good enough" for DD.)