This report synthesizes findings and draws lessons about the implementation and results of the "No Child Left Behind Act of 2001" ("NCLB") based primarily on two longitudinal studies funded by the U.S. Department of Education. Progress to date suggests that "NCLB's" ambitious goal of having 100 percent of U.S. students proficient in reading and mathematics by 2014 will not be met. In addition, the flexibility provided to states by the law has resulted in the establishment of a different accountability system in every state, each with different academic standards, levels of student proficiency, and teacher requirements. Parents have not responded in great numbers either to school choice or to receiving supplemental educational services options. Should Congress reauthorize "NCLB", the authors recommend that it consider making the following changes to the law: promote more-uniform academic standards and teacher qualification requirements across states, set more-appropriate improvement targets, broaden the measures of student learning beyond multiple-choice tests in reading and mathematics to include more subjects and tests of higher-thinking and problem-solving skills, focus improvement efforts on all schools while continuing to offer parental choice, and provide incentives for highly qualified teachers to teach in low-performing schools. Appendices include: (1) Data Sources for This Report; and (2) Abstracts of Reports. Individual chapters contain footnotes. (Contains 1 figure.) [This paper was written with Paul Steinberg. This paper was prepared for the U.S. Department of Education. For the companion report, "What Can We Learn from the Implementation of "No Child Left Behind"? Research Brief", see ED509398.]