High-quality studies find that charter schools boost achievement by more than their traditional-public-school counterparts—an advantage that is particularly large for students of color in disadvantaged urban communities, and one that has only grown larger as the charter sector has expanded and matured. For example, a June 2023 study conducted by the Center for Research on Education Outcomes (CREDO) estimated that students who attended charter schools, on average, “advanced their learning in math by an additional six days in a year’s time, and in reading added sixteen days of learning,” compared to their traditional public school counterparts. Furthermore, “charter students in poverty had stronger growth, equal to seventeen additional days of learning in math and twenty-three additional days of learning in reading, than their [traditional public school] peers in poverty.”
Understandably, some are skeptical of these results. Yet evaluations of matching approaches such as CREDO’s suggest that its estimates closely resemble those generated by a random lottery, meaning they aren’t the product of “selection bias” or unobserved differences between students in charter and traditional public schools. Nor, according to multiple studies, is there much evidence that charter schools cream the best students. (Indeed, some research suggests that charters enroll unusually low-performing students.)
Emerging research also suggests that the gains associated with charter school attendance go far beyond test scores. For example, studies have also found a positive relationship between enrollment in charter schools and long-term, real-world outcomes, including college enrollment, teenage pregnancy, incarceration, and voting.
Where the research literature is less clear is why charter schools increasingly outperform district schools. Still, it does offer some hints and plausible hypotheses.
Charter schools are more likely to embrace evidence-based practices.
In a landmark study, Will Dobbie and Roland Fryer, Jr. examined charter schools in New York City and found that five factors were predictive of their success: “frequent teacher feedback, the use of data to guide instruction, high-dosage tutoring, increased instructional time, and high expectations.” According to subsequent research, these practices also tend to be embraced by charter schools that have been grouped under the “no excuses” banner (as in, there are no excuses for not raising student achievement). And many of the best-known charter networks, such as KIPP, Success Academy, and Achievement First, rely heavily on some combination of them. Now that schools run by such networks account for at least 40 percent of the charter sector, their embrace of evidence-based practices could be a major factor in the success of the sector writ large.
Charter schools are more likely to maintain diverse and effective teaching staffs.
In theory, freedom from district bureaucracies and teachers union contracts should allow charter schools to make better hiring decisions, appropriately reward strong performance, and part ways with ineffective teachers when necessary. And there’s some evidence of precisely that happening in the real world. For example, one recent study finds a strong relationship between performance and retention in New Orleans’s “market setting,” while a recent Fordham Institute study found that charter schools in Pennsylvania were more likely to promote their high-performing teachers into leadership roles. Another Fordham study found significantly lower rates of teacher absenteeism in charter schools than in traditional public schools—a sign of more effective management that could also help to explain charters’ strong results, given the negative impact of teacher absenteeism on student learning. Finally, yet another Fordham study found that North Carolina charter schools were more likely to have diverse teaching staffs than their district peers, which allowed for more frequent matching of Black students with Black teachers who tended to boost their achievement.
Charter authorizers have closed low-performing schools, including in states that used to have low-quality sectors, like Texas and Ohio.
For example, another landmark CREDO study found that at least 300 low-performing charter schools closed between 2006 and 2012—a phenomenon that likely contributed to the sector’s gradual improvement during that period. Closure has also played a visible role in the handful of states that used to have low-performing charter school sectors. In Ohio, for example, charters’ impact on achievement went from negative to positive after a 2015 policy change that ramped up accountability on charter authorizers and led to dozens of school closures. Similarly, in 2013, Texas simultaneously boosted funding for all charter schools and moved to close its lowest-performing schools. Following the law’s passage, CREDO’s estimate of Texas charter schools’ effect on math learning went from negative seventeen days per year (for 2012–13) to positive seventeen days per year (for 2014–15), with even larger gains for poor students and the state’s ever-expanding Latino population.
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To be clear, everyone involved in education should root for all schools to succeed, regardless of sector. One hope for charter schools, in fact, was that their innovative practices might migrate into traditional public schools (and Roland Fryer led a project to encourage exactly that in Houston, with some success).
Still, there’s little doubt that educators in most districts face significant challenges in adopting promising practices, from burdensome teachers union contracts, to dysfunctional central offices, to meddlesome school boards. By wiping the slate clean of these impediments, policymakers have given charter schools the chance to dramatically improve student outcomes. Thankfully, many charters are seizing the opportunity.
