The authors’ Brookings blog Post, they explain their peer-reviewed work. The major conclusion is:
We find the impact of attending a virtual charter on student achievement is uniformly and profoundly negative, equating to a third of a standard deviation in English/language arts (ELA) and a half of a standard deviation in math. This equates to a loss of roughly 11 percentile points in ELA and 16 percentile points in math for an average virtual charter student at baseline as compared to their public school peers (see Figure 1 above). There is no evidence that virtual charter students improve in subsequent years. We could not “explain away” these findings by looking at various teacher or classroom characteristics. We also use the same methodology to analyze the impact of attending brick-and-mortar charter schools. In contrast, we find that students who attended brick-and-mortar charters have achievement no different from their traditional public school peers (see Figure 2 below). Our confidence in these results is further buoyed by other studies of virtual charter schools in Ohio and nationwide having similar findings.