Chakra control is one of the Basics of being a ninja, below is the explination by Ebisu after the Chunin Exam preliminaries
Ebisu admits that this example is an understatment of Naruto's abilities but that it gets the point acrossed, Naruto askes why he does better then both Sasuke and Sakura some times; Ebisu replies with the fact that Naruto has more stamina then them, what he doesn't mention to Naruto is that its because of kyruubi, the Nine-tailed fox.
