Girls appear to be better students
...because they tend to be better at sitting still for long periods of time and suppressing their need to burn off energy. But if girls are such good students why doesn't it translate into better careers?
Just as I think there is a subtle bias against women in IT I also think there is bias against boys in the typical school environment, at least at the elementary level.
Unfortunately there is bias whereever you look. The only way to improve things is to expose the issues so they can be addressed.