The current model is that 20-30 kids who want to be moving around and interacting with each other are forced into seats and restricted from moving for hours while teachers talk at them until they get distracted and zone out the teacher to think about other things. And then they go home with an assignment to complete which they may or may not do depending on how motivated they are. When Khan Academy flips this, they make much better use of the situation. There's no reason for everyone to be lectured at together, but there's every reason to allow students to interact and work together while solving problems. There's very little motivation to go home and complete a rigorous assignment when you can be playing outside or watching TV, but watching a couple 10-20 minute videos is enjoyable and completely digestible.

Personally, I believe that the act of working through problems is often more important to learning and development than watching or listening to lectures explaining how to work through problems. If a student's conditions at home are so unstable that they cannot concentrate on watching a single video, then they are clearly never going to be able to put a reasonable amount of effort into homework assignments in the normal education system. I would rather they fail to watch Khan videos at home and interact and explore exercises in class than listen to lectures in class every day but never put those skills into practice because they fail to do homework at home. However, yes, availability of computers at home is an issue. It would be great if Khan Academy were the cure-all for education and would be perfect for everyone, but this is never what has been claimed; unfortunately, for the time being, Khan Academy is not a viable solution for those without computer access.

I'm not sure if the phrasing of drilling exercises was supposed to imply something negative, but the goal of KA's exercises is not to drill students on a question until they can answer it as quickly as possible (this is what I think of when I think of a drill). The goal is to allow students to explore and advance at their own pace, proving mastery of a concept covered in a video and then feeling confident to move onto a more advanced topic. We try to make the exercises as modular as possible (which may make them outwardly resemble drills), but we do this so a complex problem can be broken down into many smaller and easier problems. Instead of making a staircase with huge steps that would take a giant to leap, we're making a staircase with small steps; that way, everyone can advance at their own pace.