Nothing could be further from the truth. After 3 years of art school, I can confidently say that art school is for self-motivated, self-taught people. The students who flourished and developed during their time at AAU are the driven ones, the ones who love what they do, who make personal work outside of class, who love talking about art with their friends, who go to conventions, who email teachers for advice. The ones who didn't were the lukewarm, insecure, bored, complaining students.
In the world of art, there are no successful unmotivated artists. Whether you attend art school, are self-taught, or a combination of the two, you need passion and hard work. Art school is not a substitute.