In the end, it's not about the students, but about the teachers. Whatever environment that is easier for teachers to control their situations would yield better academic results. The key factor is homogeneity. In other words, ANYTHING that increases homogeneity would be better for academic achievement simply because it's easier for the teachers to manage. Diversity or heterogeneity has the opposite effect. The academically worst scenario is a class consisting of hugely diverse students: different genders (including gays and lesbians), different age groups, different IQ levels, different cultural backgrounds, different income levels, etc... The teacher in such a classroom won't be able to assume anything to be in common among them, and so teaching one simple thing would be far more time-consuming than it would be in a homogeneous classroom. This was painfully obvious in high school when I first moved here from Japan.

So, they should not be surprised by this finding. This isn't about gender; gender happens to be one of many factors that causes the classroom to be more diverse, which is bad for academic achievements. BUT, the kids might be learning something that is not academic; things that cannot be measured, such as the ability to understand human beings. In the long run, the latter might actually be more important.

It could also be argued that boys adapt better to heterogeneous situations. In other words, it's not that boys ruin schools, but that girls are not as good at handling heterogeneous situations. The reason why boys could afford to be "emotionally retarded" is because they could operate more independently. Girls are more inter-dependent; their strengths are realized through inter-connections to others. And, homogeneity encourages more inter-connections.

( I thank dyske for his balanced assessment.)