The evidence on that correlation is actually very strong. However in our society there is an effect that goes a long way to hide it. For a number of reasons (including earlier puberty), women have a significant academic advantage in high school. This means that about 60% of people heading to college are women.
So if you're in an environment with lots of young college educated young people, all will be reasonably smart (they had to be to get into college), and you have on average about half-again as many women as men. If you just take this population and look for the top quartile, women are still over-represented relative to men.
What about the smart men that I said existed, where are they? They are everywhere. It turns out that if your IQ is in the top 2%, you have worse odds of finishing high school than if your IQ is median. Lots of smart people make it nowhere near college for various combinations of reasons. If you mostly hang out with college graduates, you might never notice that, for instance, there are some really smart car mechanics out there.