Is this a good place for a discussion on what high school coaches do that causes athletes to stop growing after high school?
there are multiple reasons.
sometimes a kid has just reached their ceiling for some reason or another.
sometimes a kid goes to a college program that doesn't give them everything their high school program had. (training, motivation, attention, etc.)
partying/motivated by things other than running.
injuries.
But what does a workload look like that will cause a kid to stop improving at 18 years old?
Also, there is an argument that if a kid isn't going to progress well beyond high school, it's likely they were never going to be all world in college. Maybe the heights they reached in high school were worth it.