In recent decades testing has become a much more visible and high-stakes accountability mechanism that is now seen as a powerful tool that can be used to drive school improvement. The purpose of this book is to identify and analyze the key issues associated with test-based educational accountability and to chart the future of educational accountability research. Chapter contributions are intended to be forward looking rather than a compendium of what has happened in the past. The book provides an accessible discussion of issues such as validity, test equating, growth modeling, fairness for special populations, causal inferences, and misuses of accountability data.