School size is a related factor. For example, Harvard is not going accept 50 applicants from the same school, even if it's a relatively large and exceptionally

School size is a related factor. For example, Harvard is not going accept 50 applicants from the same school, even if it's a relatively large and exceptionally competitive one like Stuyvesant in NY or Thomas Jefferson in DC. But Harvard will totally accept 8-10 applicants from a small exclusive private or parochial school. The ratio plays in favor of smaller high schools if (say) the population of students going to any one college is capped at 5% for a large school and 10% for a small one. This bears out in what I've observed (all anecdotes ofc). Many people who go from these sorts of large south bay high schools to top-5 UCs are head and shoulders smarter than the graduates of the small private school => Ivy League pathway, despite the Ivy schools ranking better. When you see it in action (brilliant kid who went to a large, highly competitive public high school who was rejected from every Ivy, and is way smarter than many students who went to the schools that rejected them), it feels rotten. Happily most of the folks I've met in this category have great careers but their confidence often takes a hit at the age of 17-18.