[theorique]

I'm saying it only takes one kid who makes an inappropriate joke like changing "public void" to "pubic void" when we're doing a code review. In such a situation, the boy will suppress a smile while he innocently exclaims he made a typo, while his friends all giggle innocuously

This is an expression of "masculinity", pseudo- or otherwise?

Seems more like a silly juvenile joke that some kids (or adults) of both sexes might enjoy, and some might roll their eyes.

[obstacle1]

I thought this too. There is nothing inherently masculine about pubic hair, or jokes about said hair.

[theorique]

I mean, if you made me guess the sex of the person involved, I would certainly suspect it was a boy. Mischief of this kind tends to be more popular among boys. But a joke like this isn't intrinsically sexist, or anti-girl, or silencing of female voices

(Obviously, it's good if genuine sexism is halted in coed classrooms so that both boys and girls can learn.)