The effects of "transitional-bilingual" and "dual-language" educational models on proficiency in students' home language (Spanish) were examined in a study of English language learners in the first and second grades in a large urban elementary school. In each grade, students were taught with either a transitional-bilingual model or a dual-language one, with a Spanish proficiency assessment administered on a pre/post basis. ANOVA results showed that both models produced significant increases in multiple dimensions of Spanish proficiency (alphabet/sight words, reading, writing, listening, and verbal expression). However, second-grade students in dual-language classrooms (who had longer exposure to the instructional model relative to first graders) scored significantly higher in verbal expression skills. In light of research linking proficiency in the home language with achievement in English language skills and content learning, dual-language instruction appears to be more effective than transitional-bilingual education, although the advantage is limited to the facilitation of home-language verbal expression associated with the dual-language model.