California charter schools outperform traditional public schools in reading but significantly lag in math, according to a national study released Monday by researchers at Stanford University.
The study of charter schools in 15 states and the District of Columbia found that, nationally, only 17% of charter schools do better academically than their traditional counterparts, and more than a third "deliver learning results that are significantly worse than their student[s] would have realized had they remained in traditional public schools."
"We find that a pretty sobering finding," said lead researcher Margaret Raymond, director of the Center for Research on Education Outcomes.
Charter schools have been widely scrutinized, but the Stanford study was one of the broadest and deepest attempts to come to grips with their progress, in part because the researchers were able to look at test scores down to the level of individual students.
In California, the study found that charters overall did about the same as regular public schools, with reading gains more or less balanced by the math deficit. But the researchers stressed that charter schools vary widely in quality, making it difficult to generalize about their performance.
They also said that while California students, on average, did much worse in math in their first year in a charter school, they outperformed their traditional public school counterparts after two years. They also found that several groups, including low-income students and English-language learners, did better overall in charters.
Charters are public schools that operate independently, with only limited oversight by school districts or other authorities. Intended as laboratories of innovation and excellence, they are growing rapidly and have powerful advocates in President Obama and Education Secretary Arne Duncan. There are more than 700 charter schools in California, the most of any state, and more than 4,000 nationwide.
Raymond said her center evaluated student performance at more than 2,400 charter schools in the states that agreed to participate.
"The good news is that we have a number of states" -- she named Arkansas, Colorado, Illinois, Louisiana and Missouri -- "where the average charter school performance is actually better" than that of traditional public schools. There are six states -- Arizona, Florida, Minnesota, New Mexico, Ohio and Texas -- where charters showed significantly worse performance.
Randi Weingarten, president of the American Federation of Teachers, issued a statement saying that the study demonstrates "that charter schools are not the panacea they often are made out to be, and that our national focus must continue to include discussion of how to support and improve our regular public schools."
Jed Wallace, executive director of the California Charter Schools Assn., which represents and supports charter schools, said he welcomed the report, even those parts that showed charters in less than a flattering light. Asked why California charters were doing worse in math than their traditional counterparts, Wallace said, "My sense is that we've got a lot of relatively young charter schools, and a lot of the entrepreneurial thrust and momentum is translating into progress in English arts, and math, which requires a greater sophistication in many ways . . . is just not there yet."
He added that some charter schools were "just not up to the challenge" and should be closed.
The researchers had access to individual student records, and could assess student progress over three years of testing. They were able to compare charter students who had left traditional public schools with "virtual twins" who had stayed. To do this, they matched up the charter students with all the students at their former public school who closely matched them in terms of test scores, ethnicity, family income and other factors. Then they created "twins" by taking an average of those other students' scores over the ensuing years.
This methodology drew criticism from the Center for Education Reform, a Washington-based nonprofit that is an advocate for charter schools. Jeanne Allen, the center's president, issued a statement saying that the Stanford report "fails the most important and most objective test of student data analysis through their use of virtual twins to replicate real student growth by creating 'straw men' subjects."
However, Priscilla Wohlstetter, a professor of education at USC who issues an annual report on the progress of California charter schools, said she had reviewed the study and found the methodology to be sound.
She urged the researchers to focus on why some schools do better than others.
"Let's take a look at what's making the difference," she said. "What are the educational strategies that are being used in the high fliers, or in the ones that consistently don't do well?"