I'm beginning to think that the findings on co-ed/single sed education depends entirely on the bias of the researchers.
Just from today's googling etc I look at studies about boys it says boys thrive in single gender classes but if I look at research about girls it says that girls thrive in single gender classes but boys are better off co-ed. I'm beginning to get the feeling that many of the researchers into girls education are coming from an assumption that girls don't get a level playing field in co-ed schools however I think that assumption might be out of date. Many of the researchers into boy's outcomes suggest that the reason boys are struggling in co-ed situations and that girls are increasingly dominating university entrance is that in order to be more inclusive that pedagogy and testing has shifted to methods that are better suited to ways that girls behave in class. That it's not so much the co-ed environment but the teaching and testing methods in co-ed schools that are less suited to boys whereas a boy's school can tailor it's methods and materials to suit boyishness.
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Suspect there is something in that - the needing to tailor aspect, I mean. I remember reading about a teacher who single-handedly increased the literacy outcomes of the boys at his school by creating some kind of super-reader scheme where boys "competed" by reading and everyday someone got to wear a cape (or something like that) LOL. From memory I think they themed games in phys-Ed with the same themes in their literacy program too, so that the coolness of sports rubbed off on the class work.

Scarily enough, though, even though females might be entering uni and completing higher levels of education than males, they are still lagging behind in terms of professional promotion & salary measures. Bit O/T, but just wanted to point out that classroom outcomes and life outcomes can be quite different.