School Choice or Best Systems_ What Improves Education_ - Margaret C. Wang [14]
An extensive study of charter schools in Arizona by Solomon and Goldschmidt20 challenges the notion that charter school achievement is attributable to bias in admitting only superior students (which would be against charter laws in most cases since charter schools can generally select applicants only by lottery and then only if they are oversubscribed). The authors analyzed 157,671 test scores of 62,207 students attending 873 schools.
Solomon and Goldschmidt found that charter school students generally started off with lower achievement than their peers in traditional public schools, controlled for factors such as transferring schools, socioeconomic status, and not speaking English as a primary language. Despite their initial achievement handicap, charter school students showed overall annual achievement growth approximately three points greater than that of their noncharter peers. Charter school students surpassed students in traditional public schools on the Stanford Achievement Tests in reading by the end of 12th grade. Solmon and Goldschmidt reported that the long-term benefits of switching to charter schools outweighed the short-term disruption when the transfer occurred before eighth grade.
A third longitudinal study, by Loveless, Kelly, and Henriques,21 compared the achievement gains in 49 California schools from the four-year period, 1986-89, when they were traditional public schools, to 2001-04, after they were converted to charter schools. Enrollment data, demographic characteristics of students, and credentials and experience of teachers did not change during the conversion period, but achievement scores rose significantly. This study is particularly pertinent for education policy, given that the federal No Child Left Behind Act compels state authorities to consider, among other sanctions, converting failing traditional schools to charter schools or risk losing substantial federal funds.
A Random-Assignment Study
The Hoxby study discussed above made no claim for causally assessing effectiveness gains across time but cautiously answered the question: How do the achievement levels of nearly all charter schools and nearby traditional schools compare?
Hoxby subsequently collaborated with Jonah Rockoff 22 to produce the most rigorous random-assignment study of the effects of charter schools yet undertaken, using academic achievement data and the admission status of student applicants to the campuses of possibly the nation’s largest charter school at the time, the Chicago International Charter School, which now has nine campuses. Since the school was oversubscribed, students were chosen by lottery either to be enrolled in the charter school or to remain in their traditional schools. Hoxby and Rockoff described their methodology as follows:
Our treatment group (those who, in medicine, would receive the pill) comprises charter school applicants who drew a lottery number that earned them a place at one of the charter schools (lotteried in). Our control group (those who would receive the placebo) comprises the applicants who were lotteried out. All told, the study focuses on 2,448 students who are divided between the lotteried-in and lotteried-out groups. It’s important to realize that all of the students in the study applied to charter schools, so self-selection is the same for all of them. All that distinguishes the groups is their randomly drawn lottery numbers, so we can be confident that the groups are comparable not only in observable ways (like race and income), but also in less tangible ways, such as motivation to succeed. Currently, we can compare the progress of both groups for up to four years following their application. We are continuing the study and will report further results as they become available.