IN EVERY profession there are people who fail to practise what they preach: dentists with mouths full of rotten teeth, doctors who smoke 40 a day, accountants who forget to file their tax returns. But it is a rare profession where failure to obey its own rules is practically a condition of entry. Business schools exist to teach the value of management. They impart some basic principles—like setting clear goals and managing risk. They also teach how dangerous the business world has become. The most fashionable phrase today is “disruptive innovation”: professors solemnly warn people that entire industries face powerful new forces and that comfortable incumbents are at the mercy of swift-footed challengers. But when it comes to their own affairs, business schools flout their own rules and ignore their own warnings.