> Citation? All countries have a mix of wealthy, educated students, working class students, students whose parents are drug addicts, immigrants who don't speak the local language, etc. In my experience the US isn't that different from other wealthy countries I've lived in.

Yes, but many European countries engage in so-called tracking of students, putting them in separate tracks for tradeswork, skilled labor, and university such that the "dumb" ones aren't taking university entrance exams.

In the US this has become increasingly frowned upon by (perhaps) well-meaning administrators who feel that to do this is unconscionable. In my freshman year of high-school they had advanced academic and standard groupings in the same school, but removed this my sophmore year. They re-branded all the base-level courses as "College Prep," with "Honors" being the former advanced-track classes, AP and IB courses already being branded as such.

Of course, if you were in the advanced group the counselors and teachers would all push you into AP and IB courses but they also encouraged everyone to take the SAT and ACT tests, to apply to university, and discouraged enrolling in the trades program that the county offered (half-day academic, half-day trades classes).

This type of "everyone goes to college" mentality is why the SAT is a poor academic bellwether.