I've never been in a class where there was a female head instructor except mine - I've been teaching TKD for 15+ years, and know very few female practitioners who reach high enough rank to teach; unlike many of the women I know, however, I have never had kids... and the ones who have have dropped out at some point in the pregnancy, and few have ever come back, even though the fathers (sometimes of the same children) have come back. This leads to very few high ranking female practitioners, and therefore very few female instructors - in fact, I only know of one female head instructor who has a child, and she was the head instructor of her school for over 10 years before the child was born, so she had plenty of help when she needed it. I do think that having children has a great deal to do with finding the time needed to commit to teaching a class or running a school, and I think it is harder for women, physically (pregnancy, childbirth, nursing, sick child, etc.) and emotionally (societal pressure, the needs of the family, etc.) than for men - although that is changing as society changes, but it still takes times for MAs to recruit more female students and have them stay long enough to become instructors, so there is a time lag there.