Dan John, a VERY well-regarded strength and conditioning coach, has his own spin on youth sports, but ends up at the same place: Early specialization is a one way ticket to injury. Siting the recent, massive increase in teens requiring multiple Tommy John elbow surgeries (baseball), multiple ACL surgeries (football, basketball), Dan also makes the case for multi-sport, well-rounded young athletes. Other topics include the need to write 'Intervention,' his '4 quadrants' approach to training, 3 musts for trainers, how to periodicize training, assessment tools, and the importance of teaching the hip-hinge.
Though the discussion can get a bit technical and dense at times, I feel its important for parents to understand a LOT of these concepts, so that they can better assess the job a coach is doing, as well as their own rolls in the life of their children. Just dropping your child off at water polo practice and assuming he/she will become a great player isn't the same as watching practice, seeing what needs work, and contributing to overall growth. Knowing that there will be those times when coaches back off substantially to allow for greater gains later can also help to ease anxiety for the young athlete who thinks every session needs to be an all-out, no-holds-barred affair. Knowing that there will be those times when the work is grueling and difficult, the parent can take a more active roll in both supporting the young athlete, as well as helping to manage recovery (rest, nutrition, etc).