Overall, charter school students have higher learning gains in reading and math than their counterparts in regular public schools, says a new study by the Center for Research on Education Outcomes—or CREDO—at Stanford University.
The report found that, over a period of six school years, 22 percent of charter schools had greater learning gains in reading than their traditional public school counterparts, while 25 percent of charter schools had significantly lower learning gains in that subject. Even though a larger share of the charters had lower gains than their district counterparts, on average, charter school students in New York City learned the equivalent of a month of additional instruction in reading than their traditional public school counterparts. Sixty-three percent of charter schools outperformed traditional public schools in mathematics, while 14 percent performed worse. For charter school students, those gains translated to an additional five months of learning in math compared with students in the district's regular schools.
Students in the study were pulled from grades 3-8, since those are the continuous grades when students are required to take state standardized achievement tests in reading and math. High schoolers were also included in the math analysis whenever they took end-of-course exams in continuous years (for example, if they took the Algebra I exam in 9th grade and the Algebra II exam in 10th, then those scores would be included in the analysis).
Students in charter schools in Harlem outperformed students in the traditional district schools, gaining an average of seven additional months of learning in math, but saw lower gains than the average charter school in reading. Harlem charter students' gains translated to less than a month's worth of additional learning in reading than students in the traditional district schools. The report includes a special section that delves further into data from charter schools in Harlem.
The report analyzed charter school performance in New York City from 2005-06 until 2010-11.
Charter schools enroll about 30,000 students in the 1.1-million student New York City school district. The demographics of the charter school student population differ greatly from those of the traditional district schools. Charters educate a higher percentage of African-American students than the district as a whole—62 percent compared with 29 percent, respectively—and tend to enroll fewer special education students (12 percent) and English-language learners (5 percent) than the traditional district, where special education students make up 17 percent of the population and English-language learners account for 14 percent. The report says the causes of these differences are unknown but may result from different ways of categorizing students with special needs.
The organization will release the results of charter school performance in New York state overall as part of its updated National Charter School Study, which is scheduled to be released later this year. The forthcoming national study explains the recent flood of research evaluating states' charter school performance, including Michigan, Indiana, and New Jersey. A 2009 version of the National Charter School Study is currently available from the CREDO website.
The researchers used a "virtual control record" in which students in charter schools are compared to their "virtual twins" who attend regular public schools the charter students would have otherwise attended. Twins are chosen to match the charter school student's standardized test score, race and ethnicity, special education considerations, free-or-reduced-lunch participation, English proficiency, grade level, and grade retention, in order to compare performance at the two sets of schools.
A recent CREDO study regarding the growth and replication of charter schools, recently came under criticism from school choice advocates the Center for Education Reform, which also criticized the methods CREDO's researchers used to create the center's National Charter School Study in 2009.