Castañeda v. Pickard (1981) mandated that educational programs for emergent bilinguals be tested for program efficacy. Since English language development (ELD) curricular materials are one part of an instructional program, we assess this mandate by examining the effectiveness of ELD materials in Texas. Using local linear matching, we find that schools that do not purchase any ELD curricula have significantly lower English language proficiency scores relative to schools that purchase state-adopted ELD materials. These results are robust across various matching models—inverse probability weights with regression adjustment, kernel matching, and nearest neighbor matching--and a comparative interrupted time series design. There is no significant difference between schools that adopt the two most popular ELD curricula—Rigby On Our Way to English and National Geographic Reach. This study suggests that emergent bilinguals (EBs) who attend schools that have instructional materials that explicitly foreground English language proficiency standards outperform those in schools that do not have such materials.