Why do we expect a C student to have a shot of understanding the next concept when they have gaps on a more basic one? 

At Khan Academy, we talk about turning it into a global, one-world classroom. 

Salman Khan envisions the kind of school he would like to send his own son to. In a way it resembles the one-room schoolhouses of yesteryear, where teachers and peers alike are empowered to act as mentors, humanizing the classroom.