School accountability for student outcomes is central to current policy discussions. While the policy idea is often attributed simply to the No Child Left Behind Act (NCLB), 44 states already had some form of test-based accountability when the 2002 federal accountability law came into existence. With NCLB, test-based accountability became a national strategy. It placed a clear goal on improvements in student achievement and established a series of actions and penalties for failure to meet annual improvement goals. Over 70 percent of the American public favors renewal of federal accountability legislation, and performance on similar tests is known to be important economically. In 2009, the U.S. Supreme Court focused on the importance of outcome accountability in a major school finance decision. Thus, it is inconceivable that accountability for student outcomes will disappear. But, it is also clear that the current version could be improved significantly. NCLB focuses on having all students proficient in reading, math, and science. All states had to develop rigorous learning standards and assessments of student performance, and individual schools are required to be on a path leading to universal proficiency by 2014. Research provides both an understanding of what has and has not worked and a map for useful alterations in the law. What Have Been the Results of NCLB? Because test-based accountability is generally applied to entire states, it is hard to infer what might have happened in its absence. Three separate lines of inquiry, however, provide evidence that existing accountability systems have led to larger gains than expected in a world without them. First, comparisons of math and reading performance across states from the National Assessment of Educational Progress or NAEP – often called the nation’s report card – provides some insights. Other things equal, states introducing accountability earlier showed larger gains on NAEP during the 1990’s. Moreover, students in states with stronger accountability performed better. Second, by comparing students in Florida schools graded “F” on accountability and subject to increasing sanctions with almost identical schools scoring just above at “D”, David Figlio and Cecilia Rouse find positive effects of school accountability. Finally, from results of individual state tests over time, student achievement gains tend to be larger after the introduction of NCLB than before. Although each is subject to uncertainty, the combined picture shows improved student performance after the introduction of test-based accountability. Second, accountability, particularly after NCLB, focused attention on achievement of disadvantaged populations. Evidence indicates that this feature has changed the dynamic within schools, yielding improvements in previously low performing. Third, the U.S. evidence is consistent with a growing body of international evidence pointing to the value of central exit exams and more regular accountability. Particularly where there is more autonomy in local decision making, schools facing stronger accountability pressures do better on international math and science exams. What Changes are Needed? At the same time, accountability is a relatively new invention, and it needs to be refined and improved. 1. Re-adjust state and federal responsibilities. NCLB has each state set learning standards, assessments, and proficiency levels independently with the federal government determining what actions should be taken when schools fail to make sufficient progress. This division appears backward. Under NCLB, states have chosen widely different cutoffs for “proficiency.” But, in the face of national labor markets where somebody from Georgia could well end up working in Arizona, these variations make little sense. History suggests stiff opposition to a national curriculum. But as recently seen, nothing prevents states from voluntarily joining together to develop standards and assessments. The federal government could support and encourage this. On the other hand, the diverse circumstances of schools indicate that centrally defined educational processes are unlikely to be effective. The federal government is not well equipped to determine precisely how schools do their job. Reforming NCLB could require states to develop their own plans for schools that were failing. Indeed, recognizing the heterogeneity of schools, the U.S. Department of Education has already permitted variation in plans (“differentiated accountability”) in nine states. Permitting local autonomy with central testing is, as noted above, a successful strategy consistent with international performance evidence. 2. Focus accountability on learning growth. NCLB concentrates on the proportion of students below the state determined proficiency level in each year with progress determined by comparing the percentage of successive cohorts reaching proficiency. But, schools are just one input to education. Families, friends, and neighborhoods also exert an influence so that looking just at the overall level of a student’s achievement does not capture the school’s contribution to learning. Setting accountability in terms of individual student learning growth implies that schools are assessed much more closely to their value-added to learning. Such improvements are well-recognized with 15 states already authorized to use growth models for their accountability under NCLB. Additionally, assessing growth across different learning levels rather than just at the proficiency threshold would eliminate incentives to ignore students already above proficiency or too far below to reach proficiency soon. 3. Improve assessments. The current focus on more basic skills provides advantages and disadvantages. The intent of NCLB is simply to ensure that all students will be able to participate fully in society and the labor market, but we also want to encourage and develop higher order skills. For testing efficiency, current tests are generally designed to measure most precisely a limited range of skills. An attractive alternative, however, is use of adaptive testing, which can improve measurement in the range of higher order skills. A set of screening questions moves the student to the relevant range of test questions – something easily done with computerized testing. Computerization has two additional advantages. First, it would provide immediate scoring of tests, getting around current delays in test scoring. Second, having a large test bank would permit providing each student with a random selection of questions, minimizing any chance of cheating. Indeed with a large test bank covering the range of relevant material, it would even be possible to make questions available beforehand with the notion that teachers could then productively teach to the test. 4. Fix the teacher quality requirements. Research has found teacher quality to be the most important element of a good school, and this belief led the NCLB law to require all schools to have only “highly qualified teachers.” Unfortunately, there are severe measurement problems that make prior interpretations of this requirement hollow at best and harmful at worst. Teacher quality is not captured by typically discussed characteristics of teachers such as master’s degrees, teaching experience, or even certification – things that states typically monitor. Requiring such things unrelated to student performance dilutes accountability and detracts from things that would make them more effective. Fortunately, however, test-based accountability produces the student achievement data needed to assess the value-added of teachers, a more appropriate focus of policy concerns. Conclusions Test-based accountability is now a fixture of American education, but it has also become controversial. Existing research indicates accountability has had a positive impact on school performance but also that it could readily be improved. Clearly test-based accountability does not do everything, but it is a central part to almost all serious reform efforts. Thus, improving it rather than eliminating it is the only reasonable course.