I agree with your perspective on the importance of training however you're missing a few VERY key components. As I've tried to drill into my kids, Practice makes Permanent... not perfect. Who's training your kid or kids? If you're knowledgeable enough and have the time to do it yourself (3 to 5 days a week), congratulations! If you're not... are you paying a professional trainer? Because if you have a 4th, 5th or 6th grade kid who can train on their own at the level needed to get significantly better then WOW! That kid will be special. Otherwise you're spending more money on a personal trainer, or your kid isn't improving from JUST the training.
I know some "lower level" clubs and even town programs have some excellent coaches... but the reality of the matter is the better clubs have the better coaching. Additionally, when you surround yourself (or your kid in this instance) with better players, then the coach can demand more, push the kids harder and faster, etc... hence your kid is going to develop at the game faster, be better, and gets the better "training" at practice and in games. NOW, if you want your kid to be in the top 5%, then yes, you also need to do additional independent training in addition to learning and playing the game. But (personal opinion), to state that they ONLY need to train at the ages up to 6th grade seems a little obtuse. UNLESS, you are paying thousands of dollars on private training that incorporates sport specific training, etc. Which kind of defeats your point of paying thousands of dollars to play club...
Just another opinion
Only a very small handful of the top kids in 6th grade will remain the top kids by 9th grade. Puberty is a game changer and natural athletes rise to the top. Training can only take a player so far, then size and ability become to main factors of success.
Natural athletes will always have a role, but when 8th grade hits, size rules all else. Guys, look in the mirror. If you're 5'4", your kid is probably peaking this year or next. Now look at your wife. If she is 5'1" or under, your kid has a very good chance of being tiny and, again, probably at the height of his game.
