David Kirp visits Google to talk about his book, "Improbable Scholars: The Rebirth of a Great American School System and a Strategy for America's Schools" "No school district can be all charismatic leaders and super-teachers. It can't start from scratch, and it can't fire all its teachers and principals when students do poorly. Great charter schools can only serve a tiny minority of students. Whether we like it or not, most of our youngsters will continue to be educated in mainstream public schools."