A study assessed and compared the effectiveness of two distinct approaches of bilingual education used within a single school district in El Paso (Texas). The program designs, one a traditional transitional bilingual and the other a bilingual immersion, were implemented under similar conditions of resources, school year length, class size, and other instructionally relevant variables. The immersion program used whole language, natural language, and sheltered English methodologies; the transitional program was characterized by teaching of basic concepts, basic language arts, and subject matter in the native language, with gradual introduction of English to teach subject matter and concepts. Data on student achievement were collected between 1985 and 1991 on over 350 limited-English-proficient students in 10 elementary schools, and a detailed longitudinal analysis was conducted on 230 students. Results show that in fourth grade, immersion students performed better in all aspects of academic performance, and particularly language skills, but by seventh grade, no significant differences were found in any aspect. Surveys of and interviews with bilingual program teachers, parents, and students revealed strengths and weaknesses, but general support. These results are detailed. Contains 59 references. (MSE)