This study examined the effectiveness of a transitional Spanish-English bilingual program, Academic Language Acquisition (ALA), in enhancing K-5 students' English-language proficiency, as well as their English performance in academic subject areas, in comparison with the Structured English Immersion (SEI) process. An existing reading program, Success for All (SFA), served as a confounding influence because it had similar goals for reading development and included English- and Spanish-language curricula. Given 4 years of enrollment in their respective programs, ALA and SEI students, regardless of participation in SFA, were scoring on par with one another as a group. This phenomenon occurred with content-based tests (reading, mathematics, and language arts) and in the reading and listening and speaking portions of the California English Language Development Test, an English-language proficiency measure. The only statistically significant difference among student groups was that students in both ALA and SFA appeared to be scoring at a lower level on the California English Language Development Test writing portion than matched peers in the other three groups of interest (participants in ALA but not SFA, participants in both SEI and SFA, and participants in SEI but not SFA). Additional findings, theoretical and methodological issues, and implications for future research are featured.