I want to give some perspective on this issue, I think I have an interesting perspective.
When I was in high school we had a kid who came from a family of runners. Senior year he was a multiple time state champ, ran under 4:10, was a great 2 miler and XC runner as well. He was for sure a national class runner
We also had another extremely great talent, he ran I think 1:50 or 1:51 in the 8, never really ran the mile, but I’m sure could have broken 4:10, and he was pretty good at XC as well, all state etc. another national class guy.
After this tier of guys we had guys like me who weren’t as talented, but willing to put in the same amount of work to get better. Over my years, there were a handful of these kids that were both older and younger than me. A couple 4:1x guys and 4:2x guys. Also around 9:2x and 9:3x.
We had two different coaches for track and XC, and we always had more success in track. We never won a XC title, and our coach didn’t really personalize our training at all.
I don’t think it’s unrealistic to say that a kid with average talent and a strong work ethic can be a sub 16 runner their senior year. It’s hard to get 7 of those guys on a team at the same time though.
Newbury Park’s team is insanely fast. California has so much competition, they run on fast courses, and a deep team like that breeds competition.
Most schools would be lucky to get one kid with the talent to break 15. Middle school running is really the key to success in later years.
People have this idea that elite runners can be competitive in their mid/late thirties. Sometimes this is true. Lagat, And Abdi come to mind right now. I believe both are older than 45 now.
The truth is that most guys peak at around 25-27. So if you think about it, you graduate high school and have maybe 10 years if you’re lucky.
If you aren’t running at a high level in high school, there’s less chance to get into a good college program, less chance to become a pro.
Running as a kid can make you a champion, but you need to be careful with how you structure it.