States are increasingly at the center of education policymaking in the United States. This report provides a systematic framework for assessing how much student achievement varies across observationally similar states and the extent to which changes in state performance on the NAEP are accounted for by changes in the demographics of the state. I find that similar students vary significantly in their test performance depending on the state in which they live. I also find that NAEP scores in all 50 states have increased more than would be expected based on demographic shifts between 2003 and 2013.