i disagree. i might agree vaguely that the future lies in a "pool" of the "better" kids. but my junior high vs. HS experience was that it was unpredictable within the "pool." our junior high won the area and was well coached that level. at sprints we had me and this other guy who went back and forth open races and relay leg preference. i was probably slightly faster at the races he ran then. he goes to our competing HS and gets converted to 800m. i was an above average HS sprinter. he goes to state. likewise, guy who was marginal 3rd/4th miler goes to same competing HS. our distance guys plateau. he keeps improving. he is first of the 4 to finish at XC/TF varsity meets at the end. last, guy who didn't make the 110H team most junior high meets wins area and goes to regionals as a senior HS. the key thing was he never quit showing up for practice, and when he got to HS, there's a frosh team, a JV, and a varsity, and he finally got meets -- even if it was frosh stuff -- and started progressing. i think the first two surprises were semi-predictable within the known "talent pool." i think no one saw the hurdler coming at all -- he was pulled out of a PE class to run track in HS based on 50 yard dash times, and he was well down the pecking order when that started.
what i will say is everyone who made those moves were hard workers with natural gifts. the hurdler was a tall kid who kind of grew into a frame at the end and got more athletic.
sorry but to me the moral is widely invest and see what happens. learn to coach all the events -- or delegate to others who do -- where you're like our competing HS coach where your charges improve more than mine do. i see coaching as something that matters at the margins but if we're talking 20 seconds on a 5k or 10 seconds on a mile, that can help decide who wins races and who gets recruited harder.
personally my favorite coaches knew every kid's name, knew the parents, and whether they are the future of american TF or not, could diagnose their good work and what needed help. effort, technique, etc. lousy coaches, to me, identify the supposed obvious ones, "saddle them up," and almost disdain the rest. and they might get some success out of those couple kids, and take credit for talent, but they won't win the championship meet because they aren't that interested in the small points, the kid taking 7th in triple jump, the 2nd leg on the relay, the pole vaulter, etc. you win as a team IMO when every last oar is pulling as hard as it can in its race, 5 points here, 10 there, 15 because a few kids score.
any idiot can saddle up the kid running 11s 100ms in junior high. this is not making anyone else better.