A few years ago, I heard Robert Duke (who was once a band teacher) tell a story about how he flipped practicing, and got his students to beg him to be allowed to practice more.
Essentially, he told his students that they were not allowed to take their instruments home, until he had heard them play individually and gauged whether they could practice effectively and avoid developing bad habits. Full story.
Noa Kageyama (The Bulletproof Musician)
Weblink : http://www.bulletproofmusician.com/
Photo credit : http://www.musicreadingsavant.com/