The recent CREDO study of New Jersey charter schools showed positive results for charter schools across the state, and really quite remarkable results for charter schools in Newark (read more about the study here, here, and here). The findings come on the heels of a couple of additional reports from CREDO since the large study in 2009 that showed positive results for charter schools in Indiana/Indianapolis and New York City.
Here’s our prediction: studies that show positive results for charter schools may be foreshadowing positive results to come. And we make this prediction based on evidence from studies over the past decade. Take a look at the figure below.
The figure plots out the impact from charter school studies released, by year, that qualified for the Betts & Tang meta-analysis, with the addition of significant studies released in 2011 and 2012. All of the studies used student-level, longitudinal data to compare the performance of students enrolled in charter schools with their counterparts in traditional public schools. The large circles indicate results from studies that used randomized field trial lottery designs and the smaller circles are results from studies that used other quasi-experimental research designs (e.g., student fixed-effects, student matching). The triangles represent results that were not statistically significant, but are included to demonstrate the direction of results. The dotted lines represent the overall effect sizes (ES) from the meta-analysis, by grade level and subject area.
The distribution of effect sizes indicates that findings from high-quality studies on charter school performance are trending positive, and getting bigger in more recent years. The dotted lines, which show the overall effect sizes from the meta-analysis, confirm this trend. In general, the meta-analysis found positive and statistically significant results from charter school studies for elementary and middle school grades. So it would not be a surprise if future studies show a similar pattern.
What could explain the upward trajectory in charter school performance effects in newer studies? There are a lot of possible explanations—here are just a few:
- The charter school sector is maturing. While making sure that low-performing charter schools are closed is a priority (see NACSA’s One Million Lives Campaign), authorizers, charter support organizations, up-and-coming school leaders, and charter schools that want to replicate are getting better at identifying the charter schools that will result in high quality learning environments. In other words, the charter sector is learning how to replicate success and take it to scale.
Other explanations are aligned with the research itself:
- Newer studies are using better data. The data in the more recent studies include longer spans of academic years, as well as data from more recent years. And the studies include data from more states. Up to early 2009 when NAPCS released this charter school research synthesis, the years covered in studies only went through 2006-07 and 14 states out of 40 with charter schools had been examined. Now, the newer studies are examining charter schools through the most recent year of available data (2010-11) and including more states (up to 23 states at last count). The possible implication of this is twofold: 1) studies that use more years of data are able to capture charter schools operating longer, and as charter schools are around longer, they get better; 2) the inclusion of more states (with newer data) means that the early results from just a handful of states don’t outweigh the impact of charter schools in more locations.
- Studies have become more sophisticated, using research designs that control for selection bias and student demographics.