Many educational policies hinge on the valid measurement of student economic disadvantage at the school level. Measures based on free and reduced-price lunch enrollment are used widely. However, recent research raises questions about their reliability, particularly following the introduction of universal free lunch in certain schools and districts. Using unique data linking the universe of students in Oregon public schools to IRS tax records and other data housed at the U.S. Census Bureau, we provide the first examination of how well different measures capture school economic disadvantage. We find that, in Oregon, direct certification provides the best widely available measure, both over time and across the distribution of school economic disadvantage. By contrast, neighborhood-based measures consistently perform relatively poorly.