The central message of this book is that educational accountability systems work-when they work-by calling forth the energy, motivation, commitment, knowledge, and skill of the people who work in schools and the systems that are supposed to support them. Accountability systems themselves do not directly “cause” schools to increase the quality of student learning and academic performance. At best, they set in motion a complex chain of events that may ultimately result in improved learning and performance. Our work suggests some ways that policymakers and school professionals might think more powerfully and systematically about the relationship between accountability systems and the results they produce in schools. From the beginning of our research, it was clear to us that schools construct their own conceptions of accountability-to whom they are accountable, for what, and how. A common misconception of policymakers is the belief that policies determine how individuals and organizations think and actwhat problems they regard as important, how they organize themselves to work on those problems, what results they regard as evidence of their success. One version of this misconception is the belief that schools were “not accountable” before the current wave of accountability policies, and now they are. Our research suggests that all schools, consciously or unconsciously, have well-worked-out ideas of accountability, and, most importantly, that they respond to new accountability policies by adjusting their existing ideas of accountability to the external influences introduced by the new policies. Accountability policies, in other words, work on the margins of existing organizational norms, structures, and processes in schools.