Catching up to that listing is pretty awesome. I’m not sure how you missed it, , and highly recommend for your next author n.k. jemisin. 3 consecutive Hugo awards (among many other). It’s not for everyone, but I’m not sure anyone else has accomplished that.
Depends so much on the kid. One learned about negative numbers when he was 6 and understood it immediately, including using them in sums, and absolute value. The other is this meme exactly in 3rd grade.