The problem is that a lot of people don't learn how to learn until fairly late in their education. Whatever clarity of thought and healthy skepticism I have developed, I give most of the credit to the great teachers who challenged me. It is misguided to tell most high school students to go and learn completely by themselves. Disregarding the motivation that school brings, someone that opts instead to study alone in their room runs the risk of fooling themselves -- the risk of not really getting the point, or not asking the right questions, or being just plain wrong (for long periods of time) without even realizing it.