That seems like a little extreme to me BP. A kid that starts at 3 and trains at a academy that plays 24/7 could be a almost at a pro or very high level at 15. Nadal was beating pro's at 14. Although that's not the norm.. I don't think any kids 18 or under will win a GS again like chang did at 17. I'm sure many pro's where beyond 5.0 at 15. Obviously chang did not go from 5.0-7.0 from 15 to 17.. Top ranked national 14yo's are atleast 5.0 or close. A kid can only do so much when he is small. A 12-13-14yo can develop very fast into a great player in only a few years. It does not take extensive 24/7 training at a academy. There is no reason why a kid who learns at 12-13-14 can not be competitive or be at a 5.0 level and be able to play with some players in a few years compared to those who have played since they where 8. It all depends on the players.