You need to think of it a little differently than only tiny percentile differences. There are 3.3m high school seniors graduating. Of these 1.8m took the ACT. 1200 or so got a 36 and 97th percentile would be about the 54,000 student. There are 14,000 Ivy League freshman each year including Cornell which is larger and a bit less selective. If you include MIT and a Stanford, the total number of freshman is around 20,000. You are correct that there isn’t a lot of statistical difference between a 33 and a 36 but small differences matter when you are talking about top colleges. My guess would be an admissions officer sees a 33 and “check” you have the standardized test scores needed so they would look at other aspects of the application. At some schools though the difference between applicants are very minute and a stronger score makes a difference. In states like California where the ACT is not as popular only stronger students would take the tests so it would tend to skew your state averages upward. Same is true for us in Illinois only its the SAT average that’s higher. I think a 36 would probably be something a Harvard admissions officer sees daily but one or two levels down at less selective schools it might be more impactful. By the way 36 is 99.93%, 35 is 99.5%, 34 is 98.8% and 33 is 97.7%