It's difficult to overstate just how huge selection bias can get in the education space. I went to a high school in the Bay Area, one of a handful in my city. (1) Houses in our attendance area were ~$500,000+x more expensive than ones right across the street in another attendance area, because our school was "better". Why was it better? Because the parents paying an extra half million dollars to get their kid into a better school were going to make sure their kid did better, come hell or high water. So there were lots and lots and lots of after-school tutoring centers, where students would get taught the highschool material in advance, so that they would already know it forward and back when they were tested on it. Which makes the school test well, and thus look better than the other schools in the area, raising housing prices. x += $100,000; GOTO (1).

The actual quality of the education was substandard, but there is something to be said for being embedded in an environment where academic failure was simply not considered an option.