It's not sexist to point out a fact: "Girls Get Better Grades Than Boys". This is almost universally true where statistics can be found, internationally and across all subjects. It's factual that girls perform better in school: you can decide what the reason for that is, but there must be a reason. It's the essential purpose of science to try and figure out the reasons - as they have here.

You then ask: Why are there just as many male academics as there are female? I would ask: Why do males fill out almost all highly skilled and/or highly paid fields, despite poorer school results on average.

This is a very important question which points out the true scale and direction of the problem.