The federal Every Student Succeeds Act (ESSA), like No Child Left Behind before it, requires states to report information on the academic achievement of students in each of their schools, both overall and for various subgroups of students. A subgroup of particular interest to policymakers and researchers is economically disadvantaged students, who, on average, score much lower on standardized tests than their higher-income peers. Economically disadvantaged students have historically been identified as those that participate in the National School Lunch Program, which provides free and reduced-price lunches (FRL) to students from low-income families, defined as those earning below 185 percent of the federal poverty line (currently $44,863 for a family of four). The use of FRL for policy and research purposes is quickly unravelling, due in large part to policy changes enacted by Congress in 2010 that expand "community eligibility," which allows schools with at least 40 percent of students identified as eligible for FRL to provide free lunches to all of their students and eliminate paper applications going forward. As a result, many schools will be unable to report student achievement for their FRL students. Successful ESSA implementation will require the federal government to take the lead, through guidance and regulations, in suggesting feasible and uniform ways for schools and districts to meet their obligation to report the test performance of their economically disadvantaged students. New measures could include existing data on participation in means-tested programs, such as food stamps and Medicaid, or direct measures of socioeconomic status collected by states through new links between administrative data systems. A failure to quickly identify and implement new measures of family background will render policymakers and researchers unable answer important questions and comply with federal education law. Endnotes are included.