Shantanu Sinha:

Students need to be given the opportunity to take ownership of their learning
One of the most striking changes we often see in Khan Academy users, particularly historically underperforming students, is a dramatic increase in engagement, confidence, and ownership of the learning process. Many people assume personalized learning works best for high-achieving students who are self-motivated. However, we regularly hear stories like these from Oakland Unity, on dramatic changes in student study habits and overall confidence.
It turns out that you can turn a demotivated student into a motivated one when you actually give him the opportunity to succeed. The traditional one-size-fits-all classroom approach takes a student who fails a test, slaps him with a poor grade, and moves him to more advanced topics he has no hope of understanding. It is almost comical that we ever thought this would work. Not only are we pushing the student forward inappropriately, we are telling him he is a bad student and breaking his confidence.
Our approach with Khan Academy is fundamentally different. We allow students to jump back to the material they need help on. They can take as long as necessary to actually learn it. They gain a sense of success and accomplishment when they progress, no matter where their starting point was. They finally see a path in which they can improve, and they take responsibility for their learning.