The use of school accountability in the United States to improve student performance began in the separate states during the 1980s and was elevated through the federal No Child Left Behind Act of 2001. Evaluating the impact of accountability is difficult because it applies to entire states and can be confused with other changes in the states. We consider how the differential introduction of accountability across states affects growth in student performance on the National Assessment of Educational Progress (NAEP). Our preliminary analysis finds that: 1) accountability improves scores of all students; 2) there is no significant difference between simply reporting scores and attaching consequences; and, 3) while accountability tends to narrow the Hispanic-White gap, it tends to widen the Black-White gap in scores. The last finding suggests that a single policy instrument cannot be expected to satisfy multiple simultaneous goals. (JEL: I2, H7, J4)