This spring, Congress is considering the reauthorization of the No Child Left Behind Act. In the 14 years since the law was passed, AEI Education has devoted extensive analysis to how it worked in practice. AEI has distilled their work into a series of brief chapters to provide a one-stop shop for understanding why the law was passed, what went wrong in its implementation, and what lessons were learned. The report presents some key takeaways such as: (1) The No Child Left Behind Act (NCLB) resulted from decades of frustration that the federal government was spending billions of dollars on K-12 education without establishing an effective way to measure the impact; (2) Although NCLB passed with a large majority, its passage required compromises that made the bill cumbersome and at odds with America's federalist system; and (3) As Congress considers reauthorizing NCLB, it should consider what the federal government can and cannot successfully do to improve K-12 education.