It is important to distinguish between two topics that have often been mixed together: (1) the properties of value-added models and (2) the effects of value-added-based policies. Most research to date has focused on the first, nearly always in low-stakes settings, and many researchers and others have drawn strong policy conclusions from that research. But at this point we know very little about the effects of policies that would use value-added scores to make decisions about teachers. That should be the focus going forward. What really matters is not the effect of individual teachers, which is what most research estimates, but the effect of a policy.