Does Bilingual Education Interfere with English-Language Acquisition? n Dylan Conger, George Washington University Objective. In 1975, the Puerto Rican community successfully sued the New York City Department of Education, mandating the city to provide bilingual education to its Spanish-speaking English learner (EL) students. The settlement, known as the ‘‘Aspira Consent Decree,’’ has been amended over time to include EL students of all language groups and now requires public schools that have at least 15 students of the same language group in two contiguous grades to offer bilingual education. Yet observational studies of bilingual education classrooms in the city document that Spanish-speaking EL students may be the only language group that receives native- language instruction, while students from other language groups who are enrolled in bilingual education primarily receive English instruction. Method. I use this dif- ference in treatment dosage to estimate the effect of bilingual education on the time that it takes students to learn English. Results and Conclusions. Students who enroll in bilingual education classrooms learn English less quickly, but the effect of bi- lingual education is the same for Spanish-speaking and other students, implying that negative selection mechanisms are at work. In 1975, the Puerto Rican community successfully sued the New York City Department of Education, mandating the city to provide bilingual education to its Spanish-speaking English learner (EL) students. The set- tlement, known as the ‘‘Aspira Consent Decree,’’ has been amended over time to include EL students of all language groups and now requires public schools in the city that have at least 15 students of the same language group in two contiguous grades to offer bilingual education (NYCDOE, 2000). Yet observational studies of classrooms labeled ‘‘bilingual education’’ for non-Spanish-speaking students reveal that many of these classrooms rely n Direct correspondence to Dylan Conger, Trachtenberg School of Public Policy and Public Administration, The George Washington University, 805 21st St. NW, MPA 601G, Washington, DC 20052 h dconger@gwu.edu i . This work is supported by the Foundation for Child Development Young Scholars Program and the data were made available from New York University’s Institute for Education and Social Policy (IESP). I can provide all pro- gramming information to those who seek to replicate the study; however, requests for data must be made to IESP or to the New York City Department of Education. I am very grateful to anonymous reviewers, Kimber Bogard, Stephanie Riegg Cellini, Jin Sook Lee, Mark Lopez, Joseph Robinson, Amy Ellen Schwartz, Leanna Stiefel, Ruby Takanishi, and par- ticipants at the Association for Public Policy Analysis and Management Annual Meeting and University of Maryland Baltimore County Public Policy Department research seminar for thoughtful suggestions. Meghan Salas and Anna Zimbrick provided excellent research as- sistance. SOCIAL SCIENCE QUARTERLY, Volume 91, Number 4, December 2010 r 2010 by the Southwestern Social Science Association