In order to become an elite athlete, a child needs to be old enough to understand what is involved. Most who specialize at a young age (before sixth grade) don't know what they are getting themselves into: a cutthroat, high-stakes, business run by adults.
Before high school, a child is not likely to fully appreciate that if she plays on a select team she may often be practicing or going to bed early, worn out after a hard day of exercise, while her classmates are watching TV or socializing, or she may be getting up early, while others are giving their growing bodies the rest they so desperately need. While some kids choose to specialize because they realize that they have a special talent and want to improve, for many student-athletes, external pressure from parents and coaches steers them in a direction they may or may not want to go. The explosive growth of travel teams for kids before sixth grade thus reflects a youth sports system promoting the values and expectations of adults and not the best interests of children.
Children who specialize early to please adults fail to develop the critical ability to say no and to know the limitations of their bodies, knowledge that comes only with age and experience (studies show that most elite athletes don't know their bodies, their capabilities, and their limitations, until the end of their careers, at about age thirty).
The enthusiasm and passion a child may show for a particular sport is not enough to justify excessive training or participation on a select team. After all, you don't hesitate to limit the amount of time your children spend on other activities they enjoy, e.g., television and video games. Why shouldn't you also place appropriate limits on the amount of time they spend playing ultra-competitive, super-organized sports at an early age? That, after all, is what parenting is all about: looking out for your child's best interests.