Relevant: stereotype threat and testosterone

The important thing here is that gender sterotypes are merely a subset of an ability focused approach. Telling kids you are smart, or that your gender does well on these tests is roughly the same thing. High-T people (competition-oriented) react very positively to an idea that they have more ability than others, and very negatively to the opposite. Low-T people don't really seem to care much.

At any rate, split kids into two class. Put the low-T kids into a class with a growth mindset, and feed high-T kids with ideas that they have superb innate ability.