For centuries, boys were top of the class. But these days, that's no longer the case. A new study by the OECD, a club of mostly rich countries, examined how 15-year-old boys and girls performed at reading, mathematics, and science. Boys still score somewhat better at maths, and in science, the genders are roughly equal. But when it comes to the students who really struggle, the difference is stark: boys are 50% more likely than girls to fall short of basic standards in all three areas. Researchers suggest that doing homework set by teachers is linked to better performance in maths, reading, and science. Boys, it appears, spend more of their free time in the virtual world; they are 17% more likely than girls to play collaborative online games than girls every day. They also use the internet more. Third, peer pressure plays a role. A lot of boys decide early on that they are just too cool for school, which means they're more likely to be rowdy in class. Teachers mark them down for this. In anonymous tests, boys perform better. In fact, the gender gap in reading drops by a third when teachers don't know the gender of the pupil they are marking. So what can be done to close this gap? Getting boys to do more homework and cut down on screen-time would help. But most of all, abandoning gender stereotypes would benefit all students. Boys in countries with the best schools read much better than girls. And girls in Shanghai excel in mathematics. They outperform boys from anywhere else in the world.