Easy, just tell everyone that anyone can study STEM as long as they work hard. Do you know Noether, Marie Curie, Grace Hopper, Chien-Shiung Wu, and many more female scientists and engineers are household names? They are featured in mass media, in text books, and in our bedtime stories.
Gender bias in STEM? That's a god damn first-world problem.
Yep. Reduce wealth and increase economic pressure enough so that survival is dependent on a finding a good job, and suddenly, magically, "bias" disappears.
"Most of the girls we talked to from other countries had a slightly playful approach to Stem, whereas in Russia, even the very youngest were extremely focused on the fact that their future employment opportunities were more likely to be rooted in Stem subjects."
Then, when wealth (and all other measures of gender equality) dramatically increase and people become free to choose to do whatever they want, largely free from economic survival pressure, suddenly, magically and inexplicably, "bias" pops up again.
Gender bias in STEM? That's a god damn first-world problem.