Garvin Foote.....he was 5'11 and weighed probably 180 pounds and was probably the fastest kid on the team. For small town Idaho, this basically made him Bo Jackson. We had basically one play on offense - hand the ball to Garvin and let him run over people. We played an eight-game season and I would imagine he probably ran for close to 2,500 yards and 30 touchdowns.
By our Senior year, with an aggressive workout regiment, he was............5'11 and maybe 190 pounds. He was a very good small school player who didn't even go on to play Division II football (he took a stab at baseball, but it didn't work out).
Point is, as you are alluding to, sometimes these kids that dominate in Jr High have just hit their peak wayyyyyyyyyy before their peers. I think Zadock Dinkleman probably fit that description. It's pretty hard to tell which ones will continue to develop and become great players in college.