Less formal professional development

In a blog post about how to improve schools, David Warlick, writing about teachers' professional development proposes that for every hour of instructional time, that a teacher have an hour of prep time. Teachers need time to prerpare for instruction and to explore new tools. He also says that in his presentations when he asks an audience of teachers "to raise their hands if they could say that they learned at least half of what they do with technology by teaching themselves," that almost all the hands go up.