That's sort of how it worked in Germany when I grew up there. At age 10 everyone gets a series of tests that decides whether they go to first, second or third t

That's sort of how it worked in Germany when I grew up there. At age 10 everyone gets a series of tests that decides whether they go to first, second or third tier schools. Only the first tier (9 years of high school) gets you admission to university. The second tier is meant to shuttle you toward vocational education, which is very good in Germany, and the third tier basically turns you into a laborer. There is some lateral movement between schools but it's pretty rare and in most states the schools are physically separated. I'm not sure what it's like now but at the time it seemed like the system didn't really sort by IQ but much more by the class you were already in. In principle it should be easy to move up but the reality is much different.