This qualitative sociolinguistic research study examines Latino/a students' use of language in a science classroom and laboratory. This study was conducted in a school in the southwestern United States that serves an economically depressed, predominantly Latino population. The object of study was a 5th-grade bilingual (Spanish/English) class. The findings demonstrate the students' awareness of their own bilingualism, their preference for speaking Spanish, and their conceptualization of English as the language of academic success. Most significantly, this study reveals how the institutional context impacts both the teacher's and the students' behaviors, resulting in an implicit institutionalized bias against Spanish.