The objective of this book is to advance our understanding of the design, implementation and evaluation of test-driven external accountability policies for improving both academic excellence and equity. This book provides new insights into debates about the efficacy of high-stakes testing through critical synthesis of previous studies and through systematic analysis of the achievement gap trends over the past 15 years. The core findings have implications for contemporary national and state policy efforts, as mandated by NCLB, to close the achievement gap. The book alerts readers to scientific, institutional and technical threats to the current test-driven school accountability system, and possible consequences if we fail to counteract those threats and continue the current policy course with underfunded mandates and an over-reliance on testing and sanctions.