Some people like to tell stressed-out students that grades aren’t super important. However, for those who are intensely focused on their future careers, maybe working to get an A on that test or being at the top of your class will be worthwhile.
Universities that are considered the most prestigious (e.g. Harvard, Yale, Princeton) are more often than not in the top-right corner for both of these graphs. This means that the overwhelming majority of their students have insanely high GPAs, were at the very top of their class, and will be making the most salary mid-career.
The plots are somewhat linear, which suggests that there is a weak correlation between high school performance, and future salary.