This paper explores the effect of accountability laws under No Child Left Behind Act (NCLB) on obesity rates among school-aged children in the United States. Our results show that pressures due to school closures for poor performance, rewards for good performance, and assistance to schools that lag behind lead to lower levels of vigorous physical activity. This effect is significant for high school children only. We find no significant impact of school accountability laws on children in grades 3 through 8 after state characteristics such as state obesity rate are taken into account. We also find that state physical education mandates increase physical activity for children in grades 3 through 8 and mitigate the negative effect of accountability pressures on physical activity at the high school level where accountability pressures are most effective at decreasing physical activity and increasing obesity. The study shows that physical education mandates play an important role in promoting physical activity for all grades in our sample.