Most musical schools start with a bottom-up teaching eg. Czerny etudes for the dexterity and the velocity of fingers. However, teachers usually go through all the etudes before moving on towards real works.
While I agree with the necessity of such basic practice and education, I wonder whether there exists an approach that is rather top-down based and goes like "OK, here's this piece; now if you want to be able to play this part, you need to practice the following exercises: ".