This thesis presents the results of a field study of code-switching in K-3 level classrooms of an experimental Spanish-English bilingual education project in Los Angeles. The goal of the project, based on a pluralistic model of bilingual education, was the maintenance of Spanish by means of continued language-development in both the students' native and second languages. The thesis shows that the means of implementation contradict the project's goals. Data was collected on code-switching in 12 different setting-participant combinations during language-development lessons. A quantitative measure related code-switching by teachers and students to specific setting-participant combinations. An analysis of the functions of teacher code-switching indicates that it is a communicative strategy. The study concludes that: (1) English is more intrusive in the classroom than Spanish; (2) the contrast in the amount of code-switching by teachers may be based on their expectations of students to communicate in the target language; and (3) the contrast between the patterns of teacher code-switching during the language lessons may be signaling to students that English functions more efficiently than Spanish for "important" messages in the classroom. Demotion of Spanish may be an attitude-motivation factor in both the maintenance of Spanish for native speakers and the acquisition of Spanish for native speakers of English. (Author/CLK)