The effectiveness of charter schools in raising student achievement has become an intensely debated issue. When we last considered this topic (10/08/2009), the Department of Education was pushing charter schools but dueling studies introduced uncertainty. CREDO had done a national study that found more charters doing badly compared to their feeder schools from the traditional public sector, and an NBER study in New York City found substantially better performance of charters versus traditional public schools. Various people began lining up with one study or the other – largely it seems on the basis of which results they liked. Those supporting expanded charters emphasized the New York results, while those generally disliking charters emphasized the other. There were two major differences among the studies: they used different evaluation methodologies, and they analyzed different sets of charter schools. The CREDO study employed a matching approach that compared students in charter schools to a virtual student who had similar prior achievement, race, income, and so forth along with being in one of the feeder schools from which a given charter drew its students. The New York study compared students who won a lottery for entry into each (oversubscribed) charter to students who lost the lottery. The CREDO study looked across 15 states (which did not include New York), while the NBER study was confined to New York City schools. Either or both of those differences could be responsible for the different results. A new study by CREDO clears up the uncertainty. They took their matching approach to evaluation to New York City charters, thus holding constant location. The new CREDO results were virtually the same as the prior NBER results: Charter schools in New York City do significantly better than the traditional public schools that feed them. Thus, it is not methodology that drives the prior differences in results, but instead it is the fact that New York City simply is doing something different. These results change the focus of debate. They bring us back to considering what is it that makes some charters fly high and others fall flat. Is it the authorizing environment? The state of existing public schools in an area? The role of state regulations and oversight? It is really important to dig deeper into the underlying causes of effectiveness across the charter sector. They will not only give us insights about how to organize charter schools but also how to manage and improve the traditional public schools.