Why do you have mixed gender workshops? Shouldn't boys be with boys and girls be with girls?
Because the evidence is overwhelming. We are more alike than different.
Because boys need to know about female bodies and vice versa. Because we need less shame and secrecy about the diversity of human bodies. Because gender is not just a binary "pink box or blue box" thing. Gender is a spectrum. Sexual orientation is a spectrum. Even biological sex occurs on a spectrum, and some people do not identify themselves as distinctly male or female.
Having said that, if a situation arises where a bunch of all girls wants a closed group workshop, we can be flexible.