The US and Chinese high school systems are diametrically opposed in their philosophy on sorting. US seems to be against the idea of sorting students by ability. Whereas China sorts academically at the high school level extremely intensively

Every Chinese student at MIT or Harvard or other top schools from Beijing is likely to come from 1 of 3 high schools; every Shanghai student from ~1 high school; and so on. The academic funnel in China starts much earlier than in the US