Since the piloting of value-added progress measures by the Ohio Department of Education in 2007, we at the Thomas B. Fordham Institute have repeatedly been asked by business people, journalists, philanthropists, educators, and others to explain "value-added" and what it means for schools and children. In order to help answer this question and others--such as "How is it used?" "Should it replace standards-based assessments?" and "Is it a fairer measurer of school performance?"--we volunteered to produce a short primer to help non-specialists understand the basics of "value-added" in Ohio.