Conceptualizations of language and language learning underlie language pedagogies (Valdés, Poza, & Brooks, 2015). The present work relies on ethnographic observation and interviews in a dual immersion (DI) bilingual program, as well as a content analysis of the research foundation of the English Language Development intervention curriculum, to show how prevalent conceptualizations reflect US monolingual ideologies and monoglossic perspectives (García, 2009a). The work further shows how such views marginalize students classified as English Language Learners, referred to here as emergent bilinguals, by excluding them from important content instruction, engaging teaching methods, and primary language instruction, all for the sake of expediting their reclassification as proficient in English.