From my experience, grades were more dependent on your willingness to do pointless busy work than any knowledge or skills you had. Girls, on average, were more willing to do that busy work. Guys tended to do better on standardized tests, especially in math, but less likely to actually do homework and book reports and things like that. While I don't doubt there was a lot of sexism from the female teachers, I also don't think that is what really causes the grade disparity. My theory would be that girls are more social creatures than guys and see grades as a social status, so will work harder to achieve them. I always scored very well on any standardized tests, but I couldn't take most school work seriously enough to put the work towards it. I hardly ever did homework. I think there is also the possibility that guys, on average, require a higher level of autonomy to function. I work harder and smarter when I'm doing it out of my own free choice. School work was not out of my own free choice. I lived in a pretty constant state of fear about grades because my dad was very threatening about them, but doing something because somebody is threatening you is terribly demotivating. I wouldn't be surprised, though, if girls are less likely to be encouraged to get good grades with negative reinforcement than guys. That is a major problem in our society in general is the idea that hostility is the best way to get what you want. Keep pushing them and if it doesn't work, then push harder. Even if things get worse. The pushing couldn't possibly be the problem itself, could it? Nah, the problem is with the lazy kid that won't do whatever I command him to do.
