A recent Economist article on charter schools, though slightly more nuanced than most mainstream media treatments of the charter evidence, contains a very common, somewhat misleading argument that I’d like to address quickly. It’s about the findings of the so-called “CREDO study,” the important (albeit over-cited) 2009 national comparison of student achievement in charter and regular public schools in 16 states.
Specifically, the article asserts that the CREDO analysis, which finds a statistically discernible but very small negative impact of charters overall (with wide underlying variation), also finds a significant positive effect among low-income students. This leads the Economist to conclude that the entire CREDO study “has been misinterpreted,” because it’s real value is in showing that “the children who most need charters have been served well.”
Whether or not an intervention affects outcomes among subgroups of students is obviously important (though one has hardly “misinterpreted” a study by focusing on its overall results). And CREDO does indeed find a statistically significant, positive test-based impact of charters on low-income students, vis-à-vis their counterparts in regular public schools. However, as discussed here (and in countless textbooks and methods courses), statistical significance only means we can be confident that the difference is non-zero (it cannot be chalked up to random fluctuation). Significant differences are often not large enough to be practically meaningful.
And this is certainly the case with CREDO and low-income students. Read More »
Charter schools in New Orleans (NOLA) now serve over four out of five students in the city – the largest market share of any big city in the nation. As of the 2011-12 school year, most of the city’s schools (around 80 percent), charter and regular public, are overseen by the Recovery School District (RSD), a statewide agency created in 2003 to take over low-performing schools, which assumed control of most NOLA schools in Katrina’s aftermath.
Around three-quarters of these RSD schools (50 out of 66) are charters. The remainder of NOLA’s schools are overseen either by the Orleans Parish School Board (which is responsible for 11 charters and six regular public schools, and taxing authority for all parish schools) or by the Louisiana Board of Elementary and Secondary Education (which is directly responsible for three charters, and also supervises the RSD).
New Orleans is often held up as a model for the rapid expansion of charter schools in other urban districts, based on the argument that charter proliferation since 2005-06 has generated rapid improvements in student outcomes. There are two separate claims potentially embedded in this argument. The first is that the city’s schools perform better that they did pre-Katrina. The second is that NOLA’s charters have outperformed the city’s dwindling supply of traditional public schools since the hurricane.
Although I tend strongly toward the viewpoint that whether charter schools “work” is far less important than why – e.g., specific policies and practices – it might nevertheless be useful to quickly address both of the claims above, given all the attention paid to charters in New Orleans. Read More »
** Also posted here on “Valerie Strauss’ Answer Sheet” in the Washington Post
Most people involved in education policy know exactly what you mean when you refer to “the CREDO study.” I can’t prove this, but suspect it may be the most frequently mentioned research report over the past two years (it was released in 2009).
For those who haven’t heard of it (or have forgotten), this report, done by the Center for Research on Education Outcomes (CREDO), which is based at Stanford University, was a comparison of charter schools and regular public schools in 15 states and the District of Columbia. Put simply, the researchers matched up real charter school students with fictional amalgamations of statistically similar students in the same area (the CREDO team called them “virtual twins”), and compared charter school students’ performance (in terms of test score gains) to that of their “twins.” The “take home” finding – the one that everybody talks about – was that, among the charter schools included in the analysis, 17 percent had students who did better on the whole than their public school twins, in 37 percent they did worse, and in 46 percent there was no statistical difference. Results varied a bit by student subgroup and over time.
There are good reasons why this analysis is mentioned so often. For one thing, it remains the largest study of charter school performance to date, and despite some criticism that the “matching” technique biased charter effects downward, it was also a well done large-scale study (for a few other good multi-state charter studies, see here, here, and here). Nevertheless, as is so often the case, the manner in which its findings are discussed and understood sometimes reflect a few key errors of interpretation. Given that it still gets attention in major media outlets, as well as the fact that the CREDO team continues to release new state-specific reports (the latest one is from Pennsylvania), it makes sense to quickly clear up three of the most common misinterpretations. Read More »
I finally saw the entire “Waiting for Superman” movie last weekend, in a mostly-empty Georgetown theatre. I went with my mother, not just because she’s a great public school teacher, but also because I needed someone to comfort me while I watched.
We both had strong reactions to dozens of things about the film, and you almost have to admire the chutzpah. It is about education – with a primary focus on teachers – and includes sit-down interviews with superintendents, parents, students, businessmen, economists, and journalists, but not one teacher.
Given all the attention that has already been lavished on it, I’ll discuss just one other thing that struck me, one which I keep hearing elsewhere. There is exactly one sentence in the whole film in which director Davis Guggenheim addresses the research on charter school effects beyond the anecdotal evidence that dominates his narrative. He notes, “Only one in five charters is excellent,” with the implication that these charters show that it can be done.
He is presumably referring to the CREDO study released last year, which is the largest (15 states plus D.C.) and arguably the most overplayed charter analysis in history (for other multi-state studies showing no charter effects, see here, here, here, and here). The CREDO authors understandably framed their results in a “media-friendly” manner – by reporting the percentage of charters that did better than comparable regular public schools (17 percent), along with the proportion that did worse (37 percent).
My first point is that 17 percent is equivalent to one in six, not one in five. But beyond that, some charter advocates have taken the remarkable step of turning the finding that twice as many charters do worse than regular publics into “evidence” that the former should be expanded. The rationale is, as Guggenheim puts it, that these “one in five” charters are “excellent,” and if we can increase that proportion, we can fix our public education system. There is only one problem: That’s not what the study says. Guggenheim is either deliberately misleading his viewers or, more likely, just doesn’t know what he’s talking about. Read More »
