The authors examined the short- and long-term effects of high school exit exams (HSEEs) on graduation rates and achievement using an interrupted time series approach. There is a positive overall effect of HSEE introduction for graduation rate trends, which is heterogeneous over time. HSEEs have a negative impact on graduation rates in the year of introduction and briefly after, which is short lived and becomes positive (but not statistically significant) over the long term. There is also a preintervention negative effect, suggesting that high schools prepare for the HSEE before introduction. There are no effects for achievement, possibly due to the lack of meaningful cross-state achievement data. The findings are robust to the inclusion of states that do not have HSEEs as a control group and also robust to controlling for No Child Left Behind introduction.