Fact-Check: Are Washington’s Charters Harming the State’s Traditional Public Schools?

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The Fact-Check is The Seventy Four’s ongoing series that examines the ways in which journalists, politicians and leaders misuse or misinterpret education data and research. See our complete Fact-Check archive.
Charter schools versus traditional district schools — this is the legal fight now playing out in Washington state, after the state Supreme Court ruled charter schools unconstitutional. (See The Seventy Four’s complete coverage of the Washington court decision, and the fallout affecting parents and educators.)
In the wake of the verdict, the president of the state teachers union cheered the decision, saying, “charter schools steal money from our existing classrooms.” And similar funding arguments are now fueling charter showdowns in other cities across the country — including a lawsuit to change the charter funding formula in Baltimore.
But is it true that charter schools harm traditional public schools? Or, as some charter advocates claim, does the introduction of charters spur competition and innovation in neighborhood schools, leading to improvement across-the-board?
Based on evidence from districts across the country and interviews with several researchers, the conclusion defies a simple us vs. them characterization: Charter schools are unlikely to have significant negative effects on student achievement in traditional public schools — and may, in fact, have small positive effects on nearby schools. At the same time, there is research indicating that charters may in fact harm school district finances.
Marcus Winters, an assistant professor at the University of Colorado – Colorado Springs, has studied charters extensively. In an interview with The Seventy Four, he explained, “My results are really consistent with the literature overall, which is that as competition from charter schools — but also from other parts of school choice — increases, we see small improvements in student performance in traditional public schools.” Emphasis on small, Winters said, and not in line with expectations from some advocates that competition1 would be a “panacea” for the system as a whole.
Similarly, research in Texas, Florida, North Carolina, New York City, and Arizona shows small benefits with the introduction of charters on nearby traditional public schools, as measured by student test scores.
On the other hand, Ron Zimmer, an associate professor at Vanderbilt University, found basically no effect, positive or negative, on achievement in two separate studies across several states. A number of other studies — including one authored by Winters — have shown similar results.
The overall research is “mixed,” Zimmer said, but “the vast majority [of studies] don’t show negative effects.”
A small number of studies have produced negative results, though, including one by Scott Imberman, an economist at Michigan State University. Imberman used a different approach than most other research, which may better isolate the impact of charter schools on neighborhood schools. He finds small to moderate decline in student test scores, but a positive impact on student discipline2.
In an interview, Imberman acknowledged that his study — which looks at a single school district — was an “outlier,” saying that most other research had effects closer to zero. “My study throws a bit of caution to the general finding,” he said.
On the other hand, a September 2014 study of North Carolina suggests that past research may have actually underestimated the positive effects of charter competition. That study looked at the impact of charter schools in grades that overlapped with traditional public schools as well as in non-overlapping grades. In the case of overlapping grades, there were significant positive results on student test scores, which may have been downplayed in past research.
The effects of charter competition almost surely varies from place to place, perhaps because of size and quality differences in the sector along with differences in underlying issues, such as how they are funded. However, research has, by and large, not looked at which set of charter characteristics are most likely to create competitive benefits.3
There has generally been a dearth of research on the long-run effects of charter competition. Most studies look at impacts over the course of one or two years based exclusively on English and math test scores. (Though some, like Imberman’s study and this New York City research, look at outcomes beyond test scores; others, like this Texas study, examine many years of data.)
It is certainly possible that the longer-term implications of charter growth may be different than the short-run ones. This is particularly true since there is evidence that charter expansion can have negative impacts on school districts’ finances, which raises legitimate concerns regarding how the two types of public schools coexist.
That said, as Zimmer points out, it cannot be assumed that harmful effects on district finances will translate to harmful effects on students. In fact, it is theoretically possible that it is this very threat to districts that will spur the competitive effects suggested by charter supporters.
Taken together, the research tells a story that’s far more nuanced that what you’ll hear in the us vs. them debates now rippling across the country: We can’t assume that charter schools have either negative or positive effects on traditional public schools, and generally whatever impacts exist will be small, as measured by test scores. Many studies find either positive or zero impacts, while a small number have shown negative effects. Questions about what methods researchers have used exist for all studies, and the long-run impacts of charter competition remain unclear. (Finally, effects will likely vary from place to place)
But ultimately, the argument that charter school expansion will inevitably harm the students who remain in traditional public schools is simply not supported by the evidence.


1. It is important to note that the effects – positive or negative — that charter schools have on traditional public schools would not exclusively come through “competition.” For example, changes in student population may drive peer effects; funding changes as a result of charters may impact schools; traditional public schools may take innovation from certain charters (and vice versa); charters and district schools may even collaborate to try to improve performance across both sectors. For brevity, though, this piece refers to “competitive effects” as inclusive of all impacts that charters have on traditional public schools. (Return to story)

2. However, it’s unclear whether that was a result of genuinely improved student behavior or changes in how discipline incidents were reported. (Return to story)

3. One exception is a working paper that studied Washington, D.C. and found potential positive effects of competition — but only on schools where the nearby charter school was of high quality. This may also explain why much of the research comes to differing conclusions. (Return to story)

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