Book excerpt: Since passage of the of No Child Left Behind Act in 2001, academic researchers, econometricians, and statisticians have been exploring various analytical methods of documenting students‘ academic progress over time. Known as value-added models (VAMs), these methods are meant to measure the value a teacher or school adds to student learning from one year to the next. To date, however, there is very little evidence to support the trustworthiness of these models. What is becoming increasingly evident, yet often ignored mainly by policymakers, is that VAMs are 1) unreliable, 2) invalid, 3) nontransparent, 4) unfair, 5) fraught with measurement errors and 6) being inappropriately used to make consequential decisions regarding such things as teacher pay, retention, and termination. Unfortunately, their unintended consequences are not fully recognized at this point either. Given such, the timeliness of this well-researched and thoughtful book cannot be overstated. This book sheds important light on the debate surrounding VAMs and thereby offers states and practitioners a highly important resource from which they can move forward in more research-based ways.