Here's a great site: ITF international junior rankings.
Nadal had a 10-1 singles record, but wasn't even ranked #1.
Djoko career record in junior: 40-11, and ranked #34 in singles.... Wow, and look where he is now.
Domijan and Klahn were ranked higher in juniors, they both reached close to #10.
Some very good players, who turned pro and made the top 50 or better had worse rankings than some top college players.... very interesting!