Well, I might be missing the point. I'm just saying this: I don't think schools teach (or even imply) that mathematicians are straight white men. And in fact, schools (pre-University) don't talk about mathematicians at all. They deal in concepts which are not associated with individuals (arithmetic, geometry, trig, algebra, calc). There's only a couple of exceptions where individual mathematicians are named in high school (Euler and L'Hôpital come to mind). It's not until university level that you start getting into theorems, and actual mathematicians show up (Cayley's theorem, Lagrange's theorem, Abelian groups, etc).