Yep. There are multiple reasons kids level off after HS...sometimes, tho, with the stud HS milers, it’s because they move up in distance in college and rarely race the mile anymore. That’s what I think happened to Ron Addison and John Zishka. They both ran unbelievably fast in HS, but never ended up breaking four. Ron went 4:05 and John 4:03 for Cleveland Rhodes and Lancaster, respectively. But the reason they never broke four, I suspect, was they didn’t run many mile races after HS.... Ron went to Tennessee then later ran for Athletics West and almost made an Olympic team in the Steeplechase. Almost broke the American record. John was an All-American for Oregon in the 5000. But then you have guys like Sam Borchers. Ran 4:02 in HS, went to a great program (Penn State). Ran the mile as his event, but never broke four. If you look at Joe Bistritz and Dustin Horder, you’d have thought they’d have been under by now, but it’s just not that easy. Sub four may happen more often these days, but it’s still extremely difficult to run 3 back to back 60’s and then tack on a 4th lap in sub 60. Just ask anyone who has tried it! It also takes a pretty special set of physical track tools, including (usually) a good program and a good coach. Most runners, no matter how hard they work, are not blessed with the physical tools AND the program/coaching.