JP has a pretty good breakdown. When the kids hit 13, dads suddenly become bumbling idiots and the kid knows everything. It's a good time for a new coach.
I do, however, think that development starts young. I could only take my kid so far. We got lucky and joined a team at 10 coached by a dad you used to play in college. More importantly, he had baseball in his blood. He introduced my kid to a catching coach that he still sees 5 years later. These guys gave him a foundation to build on. Not just skills like throwing and fielding but hard work, discipline, dedication and how to look the part. When these kids are in a group of players from other teams, you can see the difference. That coach left the following year and it just wasn't the same. By 14 we found the next coach who could make a difference. A younger version of the first. It fits JP's model. Focus on the finer points.
Bottom line though, the kid has to put the work in.