Leaders in schools, districts, and states, along with policymakers in Washington, D.C., are focusing new energy on closing long-standing gaps in performance that separate low-income students and students of color from others. It's critically important that their efforts succeed--for students, their families, their communities, and for their democracy and future prosperity. Indeed, one recent estimate compared the achievement gap's impact on the economy to that of "a permanent national recession." Given the high stakes, educators and policymakers need the best information available to learn the true measure of achievement gaps and make progress in closing them. This brief explores the pitfalls in gauging gaps simplistically and suggests four ways to gain a more sophisticated, comprehensive, and accurate picture. It then illustrates these approaches using data from the National Assessment of Educational Progress (NAEP) to show how some states are making progress in closing gaps--and others are not. (Contains 9 notes.)