All of us want to make sure that the educational opportunities that we provide our children are going to meet their needs and those of our society. But how to translate that goal into national policy and the real world of the classroom is hardly unanimous - largely because the translation is itself rooted in personal convictions and assumptions that are often without any solid empirical research support. We assume, for example, that classroom time that is not "on task" is really time wasted and that students will learn more if they were kept busy and focused every minute of the school day....