As for the gender breakdown, in my limited interactions with the gifted classes it appears that girls are slightly better represented than boys, at something like 8:7, which lines up nicely with overall population ratios. If I had to guess why they seem to be breaking stereotypes, especially in the gifted math class, I'd suggest that the district is getting to girls before they've experienced enough gender pressure in general classes.

If there's anything to my entirely unscientific observation, it could become a strong argument for pushing services to well before 3rd grade (as if there weren't a ton of good arguments for that already).