The purpose of this paper is to promote clearer understanding of the graduation-rate debate by distilling the policy developments and controversy surrounding the measurement of these rates over the last decade. The paper concludes with a discussion of the move toward a federally mandated common metric for graduation rates. The No Child Left Behind (NCLB) Act of 2001 required states to include such rates as a factor when making "Adequate Yearly Progress" (AYP) determinations for high schools. Yet it allowed great discretion in how graduation rates were measured and how much progress states had to make over time. This in turn led to growing interest in a common graduation-rate measure for all states, a goal that was embraced by the governors several years ago and then codified into federal regulations in 2008. In some respects, this means that the original "graduation-rate debate" has been settled, in terms of measures and metrics for state, district, and school graduation rates. But there's a new debate on the horizon--whether and how to use those rates as a part of school accountability systems. Is it possible to do so without creating a new set of unintended consequences? What does it mean to be a "high school graduate" anyway? This paper answers these questions. Appended are: (1) Additional Graduation-Rate Data; and (2) Glossary. (Contains 5 figures, 6 tables, and 56 endnotes.) [This report was a joint venture between the Thomas B. Fordham Institute and its sister organization the Thomas B. Fordham Foundation.]