Dual language instruction (DL) is a version of bilingual education that renders instruction in two languages in the same classroom. It differs from the more common English-only classroom with pullout/separate services for students learning English as a second language (ESL). It also differs from language immersion in which students receive all instruction in their non-native language. Little is known about the efficacy of the DL model, but a recent study in the Journal of Education Finance and Policy provides some useful insights.
It makes use of oversubscribed lotteries for two DL magnet schools in the Charlotte-Mecklenburg School District in North Carolina, enabling analyst Andrew Bibler to compare the average differences in test scores between those who won and lost the lottery. In both schools, 90 percent of instructional time in kindergarten is in Spanish; in grades one to five, at least half of the content is taught in both Spanish and English. The students are a mix of both English-proficient and English learners (ELs). The sample includes students entering kindergarten from the 2006–07 through 2011–12 school years who submitted an application for a DL school. Bibler utilizes eight years of lottery results, and his primary outcome of interest is end-of-grade exam scores.
The sample includes roughly 372 observations from the English-proficient sample and 232 from the English learner sample. Overall, attending a DL school leads to increases of 0.04 and 0.05 standard deviations per year on math and reading exam scores, respectively. Interestingly, the effects for EL and non-EL students are similar. Estimates show that the effects on math scores are also similar for males and females in the non-EL sample. For the EL kids, math and reading estimates are larger for males but not significantly so.
Bibler is unable to estimate effects by race in the EL sample because virtually all of the students are Hispanic, but in the non-EL sample, estimates for math and reading are positive across all races. Next, he examines whether the DL effects can be explained by observable classroom differences, looking at such factors as average teacher experience, class size, percent of peers who are ELs, percent of economically disadvantaged peers, and percent of peers who are White. He finds that, in general, none of these examined characteristics is likely driving the positive impacts of DL.
Because his original estimates can’t distinguish between a DL-specific effect and the average effect of winning a seat in a magnet school—which is pretty important!—Bibler compares results with non-DL magnet schools, finding that the effects for the DL schools are two to three times larger than the effects for the non-DL schools. Finally, he finds no evidence that attending a DL school changes the likelihood one way or another of being classified as an English learner in grades four through six.
Unfortunately, the analysis is not able to examine the effect of DL participation on fluency or literacy in the partner language to try to parse out whether and how that may play a role. Still, this report paints DL education as a promising route by which to leverage the home language ability of EL students while at the same time educating ELs and non-ELs alike.
SOURCE: Andrew Bibler, “Dual Language Education and Student Achievement,” Journal of Education Finance and Policy (October 2021).
