I recently wrote about Ada Lovelace Day and I mentioned in passing that girls tend to initially surpass boys at mathematics in school. Then something happens, and girls almost entirely disappear from maths and the sciences. I vaguely remembered reading about this divergence in maths abilities as children progress through school somewhere, and went looking for sources. It seemed like there was this clear cause and effect thing going on: girls disappear from the science disciplines at school for some reason, resulting in a gender imbalance in related careers. After writing that, it seemed like a gross simplification, and I thought I’d try and find out a bit more about what’s going on.
First, some more simplification:

Courtesy of xkcd.