I totally agree with you Mia and my DS7 is exactly the same - vastly further ahead in reading than math, although really I think math is going to be his strongest area at the end of the day.
It's much easier to have exposure to a lot of different reading sources than fill holes in math. I have DS working 3rd grade math right now (going into 2nd), and it's filling holes. A lot of it he really does "know" conceptually but maybe isn't familiar with notation. Ah ... one of the things we hope to fix somewhat by homeschooling. Anyway - it's much more about how they learn, rather than what exactly they know IMHO.
I think the notation thing is huge -- it took me a long time to realize that even though KG could add and subtract double digits in his head, he didn't know what the signs were until last year! Duh.
With reading, it's fairly cut and dry--they can read it with comprehension and answer questions, or they can't. Of course, there's the issue of inference too, but I'll skate over that. :-)
With math, I think there's more gray area since math is essentially its own "language." If no one teaches you the notation, you're seriously limited. I'd like to see the kid that figures out calculus on his own, in his head, with no formal math instruction at all! There may be one out there, but wow--that's the PGest of PG kids!
