I went... wrote:
from 5:47 (7th grade) to 4:11 my senior year. A single 5:30 should be reachable by most kids assuming they did the amount of training you indicated.
Have you seen the fat kids in schools these days? I don't think most kids could do this. When I was in high school, the BASEBALL team (supposedly athletic kids) had to run a time trial mile on the track. They had one guy who ran CC and was pretty good and he ran 4:57, but no one else on that team even broke 6 minutes, let alone 5:30. In fact, if I'm remembering correctly only two guys other than the 4:57 guy finished under 7:00. Granted they didn't run 20 miles a week, but they had to do a little bit of running for their workouts, and they were fit generally speaking. Go into that school and pick from the remaining fat and non-athletic kids, and for one thing I don't think they could even run 15 miles a week let alone get into shape enough to break 5:30.
Just because it's easy for most of us doesn't mean it is for most. I would say even that it is impossible for most. In the United States, only 5% of adults can run a mile AT ALL without stopping. I'm sure that's better for high school students, but still, MOST of them being able to run a mile in 5:30? No way.