The last decade has seen a surge in empirical research byeconomists addressing the impact of school reform poli-cies. This wave of research dates back to Card and Krueger(1992) and a series of analyses that look across the UnitedStates to test the effects of school inputs on outcomes such asachievement, educational attainment, and earnings. Many ofthese studies use either Census data (Heckman, Layne–Farrar,and Todd, 1996) or national longitudinal surveys (Betts 1996;Loeb and Bound, 1996; Grogger, 1996) to estimate input ef-fects. Since then, much of the research has turned from thenation to states and cities, using local administrative and ex-perimental data to focus on specific policy initiatives.1 Theshift in emphasis from the national to the local has enabledresearchers to incorporate greater institutional and policydetail into their analyses. Local data often follow individualsover time, allowing researchers to use empirical techniquesnot possible with pooled cross–sectional Census data. At thesame time, the administrative data provide deep coverage oflocal areas, which national surveys that sample only a smallportion of any locality, do not. While local administrative dataprovide advantages over census and survey data for estimat-ing the causal effects of some policies, experimental data al-leviate the perennial concern that correlational analyses havenot established causality. However, experiments are not easyto implement in education, they can’t be used to address alltypes of education policy, and they tend to be too small toelicit the responses generated by large–scale reforms.