Over the past several years, student growth and growth models have received a lot of attention, in both the charter school sector and the larger education community, as an important indicator for measuring school quality. Educators and policy makers alike have been won over by the argument that because measures of student growth examine the changes in performance of the same students over time, they tell more about how well schools are educating the nation's students than do measures of student achievement, or status. Several states now have "federally approved" growth measures as part of their statewide accountability frameworks, but the methods for computing student growth are many and each method tells something different. Understanding exactly what the data is telling is critical if growth models are to have value in evaluating the quality of a given school. The purpose of this "Issue Brief" is to guide authorizers in the effective use of growth data by outlining the different models for measuring student academic growth and explaining the questions that can be answered by, and the potential limitations of, each type. In addition, this Brief explores key considerations for authorizers as they evaluate their portfolio of schools using a balanced body of evidence, including growth information, and provides examples of authorizers that have effectively incorporated growth measures into their accountability systems. (Contains 1 figure and 8 endnotes.)