"(The present study) points to the importance of creating environments that reduce the impact of stereotype threat during mathematical skill acquisition by women," the authors concluded in their PNAS article. "If creating such an environment is not done, the learning deficits that result could well be cumulative, causing problems that continually worsen as development proceeds."
It seems to me that an effective way of avoiding stereotype threat is to create a learning environment where children are isolated from each other and from adults who express negative stereotypes. They have to be isolated from each other because children are always trying to categorize each other: "Herbert is good at math and he's a boy. I'm not a boy, so I'm not good at math." They need to be isolated from adults who can't keep from expressing negative stereotypes because the adults will hamper both their learning and their performance. Children also need to be shielded from media that will teach negative stereotypes.
Maybe robot tutors are the way to go....
In the meantime, I will strive to be the positive-thinking homeschooling mom that my girls need. Not that any of them will ever think that girls are "bad at math"...too many females with math degrees in the extended family. :) (That said, I do think that the male brain tends do better when one looks at the extreme high end of mathematics achievement. I don't consider that a stereotype because it's actually true. See my previous blog post.)