Back in March, noted education historian Diane Ravitch penned a blog for Education Week called “Why Are Teachers So Upset?” Ravitch, a research professor of education at New York University, is the author of “The Death and Life of the Great American School System” and was assistant secretary of education in the George H.W. Bush administration. ... The Alliance for Excellent Education says that schools and districts nationwide spend about $2.2 billion per year recruiting and training replacements.