The studies carry evidence that confirms the hypothesis that single-sex school is more effective than coed schools in reaching some (I assume there are probably more) goals of basic education, which is academic achievement. Many comments noted that social achievement is not measured.
Aside from the fact that more studies have to be done to further confirm the hypothesis or negate it, this one seems to focus completely on sex segregation. It does not take a closer look at why coed schools are worse than single-sex schools in academic results.
What I think matters more is to find out the where, when, who, why and what of coed and single-sex schools before pointing out a how (to fix academic performance). With that, we will, for instance, be able to eventually adapt the coed model to provide the same or better academic results than single-sex.
I prefer neither model. I was educated for 6 years in a single-sex environment and 8 years in a coed. I can attest that I had a better academic performance in single-sex than coed, but that should not (or could not) be the main point of discussion as I explained above. The goal is to understand de 5Ws and 1H of the education system and this article fails to do so.