Why Khan Academy Won't Disrupt The Test Prep Business

Roger Federer, the Swiss tennis great, has won 17 Grand Slam titles in his stellar career. There is nothing about the game of tennis that Roger Federer does not know. Yet Federer, like all his competitors, has a tennis coach. A good coach, Federer has concluded, is invaluable. This is why Khan Academy won't disrupt the test prep business.