Agreed -- anything under 9:30 is exceptional for a high schooler. Under 9:15 and you are looking at top-10 in most states. The best of the best are pushing under 9 minutes much more frequently these days, although I would say that is due more to the rise in sophisticated/borderline college-level training being done than any change in the natural talent level of high schoolers in the USA. The times it takes to be a national caliber NCAA runner have stayed relatively flat despite the fact that far more high schoolers are breaking 4 for the mile and 9 for the 2 mile than ever before.
I ran 9:35 in high school and eventually ran 8:30 in college (about the equivalent of 9:05-9:10). My HS mileage was never more than 50-60 a week and we never did tempo runs. We did do long runs approaching 90 minutes during cross country and in between seasons. In weeks with no big races, we would do one longer interval session (5 x mile was a staple) and a shorter one (400s and 600s). I do remember that I ran much, much faster in high school speed workouts than I ever did in college. We did some real rippers -- coming through the quarter in under 60 seconds for 600 meter reps. The closest I came to running that fast in college was 200 meter reps at around 30 seconds. I guess that's the difference between HS and college...where you're often getting roped onto the 4x8. I ran 1:57 for the 8 in HS, but never trained for anything shorter than a 3k in college.