> I'm not saying female and male brains grow differently after that age. I have no idea.
The do develop differently after that age. The transition from a child brain to the emotionally and cognitively more mature adult brain starts a few years earlier in girls than in boys.
It starts at around 10 to 12 in girls, and around 15 to 20 in boys [1].
I suspect that this can lead to difference in what fields boys and girls end up in for two reasons:
1. It may be that the best way to teach a kid depends on where the kid is on their child->adult brain transition. Trying to teach teen boys and girls in the same classes, with the same material, at the same pace might mean that half the class is being taught in a way that is geared toward people whose brain does not work like theirs does.
2. One of the big things you get better at and more interested in as your brain becomes more adult is dealing with larger and more complicated social networks. Just around the time that you are getting close to high school, and you've finally got enough background to start getting to the good stuff in STEM subjects--the girls are also getting to where social networks are a big deal to them and they put effort into growing and maintaining their network. That's still a few years away for the boys, who are still happy to spend hours alone in front of a computer. By the time they get interested in people a few years later, they are now firmly on their path to going into STEM.
I have a suspicion that we could largely close the gender gaps in STEM fields by changing middle school and high school so that boys and girls are in separate classes with separate curricula geared toward their different child-> adult brain development trajectories.
[1] https://www.telegraph.co.uk/news/science/science-news/105291...