If Anderson had bothered to read the two studies with an eye for comparing apples with rotten apples, he may have noted the alarm bells ringing over the Hoxby study, while the CREDO study notes reservations of the type that are common to this kind of large-scale longitudinal research. For Anderson to give equal weight to these two pieces of research is like saying that that the Creation Museum in Petersburg, KY is of equal scientific value to the Smithsonian Museum of Natural History in DC.
The telling press release for the Hoxby review entitled "Headline-Grabbing Charter School Study Doesn't Hold Up to Scrutiny" with links to the study may be found here. The following is the concluding paragraph from the review, itself.
As a result of the potential sources of bias and the lack of detailed information in the reports to assess the extent of such bias, it is not possible for this reviewer or other readers to determine the degree to which the estimated charter school effects in grades 4 and above are valid. Policymakers and educators should therefore not rely on these estimates until the bias issues have been fully investigated and the analysis has undergone rigorous peer review. Given the quality of the data, however, a revised version of the analysis could provide a more definitive answer regarding the effectiveness of New York City’s oversubscribed charter schools (p. 14).And below is the concluding paragraph from the review of "High Quality Charter School Report Confirms Past Research. Press release and link to the study may be found here.
The CREDO researchers noted that this report would be followed by two additional reports. The relative strength and comprehensiveness of their data set, as well as the relatively solid analytic approaches of the researchers, makes this first report a useful contribution to the charter school research base. The two future reports should add further information that will be useful for policymakers. This review does point to some weaknesses and areas for improvement, many of which represent limitations—not outside the range of limitations that are inherent in other studies on student achievement in charter schools—that should be shared in the technical report. The review offers suggestions that we hope will help improve the subsequent reports produced by CREDO based on this multi-state data set (pp. 10-11).As for the newspaper of record, the New York Times, we are still waiting almost 6 months later for them to report on the Stanford CREDO charter study. In the interest of fairness, however, it should be noted that they did report the Hoxby study before it was actually released. Jennifer Medina, 9/22/09:
Students who entered lotteries and won spots in New York City charter schools performed better on state exams than students who entered the same lotteries but did not secure charter school seats, according to a study by a Stanford University economist being released Tuesday.. . .Ah yes, the fairness and the balance of the corporate media--and this is the ultra-liberal NYTimes, mind you.