Men's Group

First, stereotypes are hard to break and are enduring. Popular literature and media have long portray women in different, lower paying, roles than men and these impact our self expectations and choices we make.

Second, access in many higher end careers are, I suspect, controlled by a "mens club" mentality which is probably perpetuated somewhat by differentiated expectations of women versus men in terms of their ability and fierceness (it doesn't have to be valid to exist).

Also, a third factor that could be nature/nurture, is that women and men are wired differently and prefer and/or are more well suited to different sets of careers. If it happens that women are more naturally capable of working with children, for example, then it might be natural that they be more likely to enter the teaching profession.