Another possible confounding factor in why SOME fields in STEM seem to lose adolescent girls is that biology drives a more social learning style for girls.

So team activities, and those with "partners" or mentors tend to be more successful at retention. There are those in Computer Science who are exploring these gender based differences with an eye toward making coding an activity that girls and young women find fulfilling enough to want to pursue.

Apparently, it doesn't take a lot of tweaking to get them there-- much of the problem is in the solitary nature of traditional programming instruction.

Schrödinger's cat walks into a bar. And doesn't.