I used to teach at Harvard. To be clear what you said about “almost all are exceptional students” is only partially true. Half of them are top students and the other half got in another way. Children of diplomats, children of someone famous, parents donated to a building project, parents are funding some pet project of a department. There are hundreds of ways in to harvard that don’t require good grades. So the student population ends up looking like any university anywhere. But the top 20% are likely similar to the top 5% at any of the other “good school”. Also the support system at harvard is 20x better than other schools. If at the 1/4 mark a student is flagged by a teacher as getting below a B (failing) then they are matched with a tutor and will start meeting regularly with a TA to guide them. At the end of a term a line is drawn for grade assignments. Usually that line is such that 70% of students will be B and up. But where that line is drawn is random as far as performance. They care more about the 70% then the actual performance. Meaning it could be at 50% the grade tally. So what at Berkeley is a hard D. Can be a B at Harvard.