Value-added models have caught the interest of policymakers because, unlike using student tests scores for other means of accountability, they purport to "level the playing field." That is, they supposedly reflect only a teacher's effectiveness, not whether she teaches high- or low-income students, for instance, or students in accelerated or standard classes. Yet many people are concerned that teacher effects from value-added measures "will" be sensitive to the characteristics of her students. More specifically, they believe that teachers of low-income, minority, or special education students will have lower value-added scores than equally effective teachers who are teaching students outside these populations. Other people worry that the opposite might be true--that some value-added models might cause teachers of low-income, minority, or special education students to have "higher" value-added scores than equally effective teachers who work with higher-achieving, less risky populations. In this brief, the author discusses what is and is not known about how well value-added measures level the playing field for teachers by controlling for student characteristics. He first discusses the results of empirical explorations. He then addresses outstanding questions and the challenges to answering them with empirical data. Finally, he discusses the implications of these findings for teacher evaluations and the actions that may be based on them. (Contains 26 endnotes.)