A new analysis of the results from 40 studies examining charter school achievement indicates charter schools are performing better than traditional public schools in lower grades but only about the same in upper grades. The study was released by the University of Washington’s Center on Reinventing Public Education (CRPE).
For the report, economists Julian Betts and Emily Tang reviewed 40 existing studies of charter school achievement and scientifically combined the results. The weight of the evidence from their analysis suggests that, “Despite considerable variation among charter schools, there is ample evidence that charter elementary schools on average outperform traditional public schools in both reading and math, and that charter middle schools outperform in math.”
Betts and Tang said their analysis should be viewed as more definitive than any single study "because it marshals all available rigorous evidence."
The average gains from attending a charter school for one year may be modest but positive gains appear to accumulate or increase as students progress through a charter system. For example, the largest average effect, for math achievement in middle schools, suggests that on average a charter school student gains about two percentile points per year relative to their counterparts in traditional public schools. That means a student who initially scored higher than 50 out of 100 students would outscore 52 out of 100 students after one year in a charter school. Although that change may seem small, such gains amassed annually over several years could be quite meaningful, according to the report.
The authors found no substantial difference on average in math or reading achievement between traditional and charter high schools or in reading achievement at the middle school level. Student achievement results can vary geographically. Some locations may have charter high schools that outperform traditional high schools, while other areas have charter high schools that underperform.
In fact, Betts and Tang indicated that one of their most important findings was that charter school effects can vary dramatically across regions and grades. For instance, while the overall achievement difference of charter middle schools may be small, a recent study of Boston charter schools found very large and positive effects. The analysis also suggests that urban charters perform better than suburban or rural charter schools, especially at the middle and high school levels.
The report singles out the achievement of KIPP charter schools. According to the studies reviewed by Betts and Tang, students in KIPP charter schools showed significant and large improvements in both math and reading, with the estimated effects being enough to move a student initially at the 50th percentile to the 59th percentile in math and the 54th percentile in reading in a single year.
In their report, The Effect of Charter Schools on Student Achievement: A Meta-Analysis of the Literature, Betts and Tang focused on the studies they believe used high-quality approaches most likely to yield valid results.
“Examining all of these results as separate parts of a whole, charter schools look to be serving students well, at least in elementary and middle schools, and probably better in math than in reading,” the authors said. “There appears to generally be more variation in the results for math than in reading.”
“Opponents and proponents are tempted to point to one or two studies that confirm their point of view. The advantage of the meta-analysis is that it looks at the entire body of rigorous research and discerns what it is saying overall,” said Robin Lake, CRPE’s associate director. “There are indeed individual studies that show charters have quality issues that need to be addressed, but on the whole, charter schools generally seem to perform well.”
Charter school accountability could enable the achievement differences between charters and traditional public schools to become further defined over time, particularly if high-performing charter schools successfully replicate their models and underperforming charters are turned around or have their charters revoked.
“In the long run, the variation we see in charter school achievement may shrink or grow,” Betts and Tang observed. “… Over time, it is possible that the number of weaker charter schools will diminish or close due to market forces, while the number of stronger charters expands.”
Due to the variance in quality of data and analysis from the studies examined for the report, Betts and Tang warned that “the findings reported here should be considered preliminary and suggestive, a launching point for further investigation rather than a confirmation or nullification of the value of charter school policies.”
The full report can be downloaded here.
