Very few public school teachers fail to get tenure, and education reformers have struggled to find an objective measurement of teacher performance. The latest rage, the "value-added analysis," is based on standardized tests of students in English and Math. Being used all over the country as a measurement of teacher performance, it is strongly promoted by President Obama's Race to the Top in Education, but remains highly controversial, as demonstrated over the past few weeks in America's second-largest school district, Los Angeles Unified. Can it help mediocre teachers do better? Can it eliminate those who never will? Can it be a weapon to weaken hard-earned job protections and silence dissent? We hear how "value-added analysis" works and why it's created a firestorm from Washington, DC to Los Angeles.