"He is reaching his current peak, but as he gets older you can count on his times to still drop. Everyones times do. Its just simple knowledge of as you get older, the more muscle you'll have and the more serious you'll be about competing."
Tell that to the thousands of runners who got slower as they got older. Can't rely on the "you'll get faster just because you will get older" line. Obviously the kids got truck loads of talent, and a good work ethic. If I were his dad/coach i wouldnt let him run much more than a normal middle schooler would run. hes got 8 years to prove what he can do, i dont think a nike agent will care in 2014 if you list one of his greatest achievements as "15:47 pr as a 7th grader." what he does now means nothing in the long scheme of things.