From the Los Angeles Times :
Do boys lose out when girls start to do better in math? Do girls' successes lead to a "boy crisis"? An important new study says the answer is a definitive no. When girls do better in society, both sexes benefit. Gender equity is good for everybody.
And boys and girls are becoming more equal, globally, in math performance. The study by Jonathan M. Kane and Janet E. Mertz of the University of Wisconsin analyzed scores from more than half a million fourth- and eighth-graders from 86 countries. It found essentially no gender differences between girls and boys in math performance.
The students came from Western and Asian democracies and developing countries, as well as Muslim countries notable for their sex-segregated classes. But the really surprising finding was that the more equal the societies were around gender, the better everybody did in math. As the researchers conclude, "gender equity and other sociocultural factors … are the primary determinants of mathematics performance at all levels for both boys and girls."