abstract: This qualitative study explores the literacy development of adolescent ELLs in three middle school, Structured English Immersion (SEI) classrooms that implemented the four-hour, English Language Development (ELD), curriculum mandated by Arizona. The context of the study is set in two elementary school districts. Participants, three middle school teachers, were observed during four hours of ELD instruction within their English-only classrooms to examine literacy practices. Data were recorded using field note observations, semi-structured interviews, and artifact collection. During the year-long study, three main questions guided the design and implementation of the study: a) what kinds of literacy practices can be documented in Arizona SEI classrooms and what do they look like; b) how do junior high teachers implement mandated language policies; and c)what perceptions do junior high teachers have toward the mandated SEI, four-hour block? A descriptive qualitative approach informed data collection and analysis; data were collected during 76 hours of observed instruction in the classroom, in-depth interviews, and collection of classroom artifacts to document the preparation provided by Arizona Department of Education (ADE) for ELD instruction. A framework of Erickson's (1986) analytic induction and content analysis served as an analytical tool to observe literacy practices and events in the classroom. Observations of instruction within the four-hour language models in the classroom offer unique insight to the literacy development of adolescent ELLs. Findings show how State language policy mandates and teachers' policy implementation have impacted learning experiences and language development of adolescent ELLs. Findings are discussed through narrative-based vignettes, which illustrate the experiences occurring within middle school classrooms with students learning English. Data reveal skill-based approaches to the literacy development of adolescent ELLs and a lack of student-centered learning in the classroom. Teachers supported ELLs with prescriptive lessons that focused on decontextualized vocabulary development. Language policy in practice reveals a detrimental experience to second language acquisition (SLA) for adolescent ELLs in the four-hour language block. / Dissertation/Thesis / Ph.D. Curriculum and Instruction 2012