Single sex schooling might appear to be an obscure issue on the sidelines of the educational policy debates of our times. But it is far from this. In fact, a sizable number of people and political organizations would like to make these schools obscure, but somehow they are "scaling up" rather than down. In 1996, there were only two public single sex schools operating in America. By 2015 there are now at least 100 public single sex schools,...