Absolutely it's at the college level. Almost all of the top guys are clean, I suspect though, and there are no teams where it's the culture and openly discussed where it's admitted to if anyone is using. It's typically those who are naturally not fast enough to win anything of substance, and in fact even when using are at best good regional runners. Every once in a while we see that wreckless character who will use it to go from 13:40-50 for 5000 down to 13:15-25.
PED use in high school probably more often than not has the opposite effect desired, as they get slower and heavier, unless using EPO. Steroids are accessible to a fair amount of HS athletes, though, so it would be silly to think some aren't trying them. Again, highly doubt it's prevalent among the best HS runners, it's the hacks that want to run fast, but never will, who roll the dice at that early of an age.