If you talk to social scientists who study gender differences (learning as well as other topics), they will point out that in most things, the variation within the categories is generally much greater than the between category difference. In other words, there differences between individual women (and between men) is much greater than the difference between women as a group and men as a group. We as a society focus in on the between category differences and use them to produce stereotypes. When, in actuality, girl's (or boys') learning styles cannot and should not be simplified to a "female" or "male" way of thinking.
I think same-sex schools work for girls for the reasons described above: less distraction and more opportunity to take on roles and activities (especially in math and science) that would might not seem socially possible for them in a co-ed institution.
