Last week, Michael Tilson Thomas was conducting the New World Symphony in Miami when he stopped the concert in its tracks. A fidgety child and her mother were in his line of sight, and he reportedly asked them to change seats. Some details remain unclear but the mom and child did more than that – they left the hall. The incident caused quite a sensation on the Internet and raised questions: What is the appropriate age for kids to start attending grown-up concerts? And how do you prepare them for the experience?