Many parents think that if they put enough resources into their kids tennis they will achieve the ranking results they seek. Here is the reality:
If you had unlimited resources and the capacity to recruit the 100 best prospects in the world to train them together at an academy, and you were also able to individualize each program to provide exactly what every player needed to reach his or her potential, after a few years you would have 100 great players, but also a number one and a number 100 in the group. Even in this small group, one player would be the best of the group and one would be the worst. That is just how it is. There is always going to be a natural order.
From the book "Developing High Performance Tennis Players"