This qualitative research study examines how Latino/a bilingual students use their linguistic resources in their homeroom classroom and in the science laboratory during science instruction. This study was conducted in a school district located in the southwestern part of the United States. The school was chosen based on the criterion that the school is located in an area considered economically depressed, with a predominantly Latino student, school, and neighborhood population. The object of study was a fifth grade bilingual (Spanish/English) classroom where English was the means of instruction. Classroom interaction was examined from a sociolinguistics perspective. The study was descriptive in nature with the objective of analyzing the students' use of their linguistic resources while participating in science learning. The results of this study suggest that the students used their linguistic resources purposefully in order to facilitate their participation in science leaning. In the same manner, it was observed the students' reliance on Spanish as a foundation to enhance their comprehension of the scientific concepts and the dynamics involved in the science lessons, with the purpose of making sense, and thus, to express their understanding (orally and in writing) using their linguistic resources, especially their English language, as it was expected from them. Further, the findings disclose the students' awareness of their own bilingualism, preference for speaking Spanish, and their conceptualization of English as the language to achieve academic success. It has also been observed how the pressure put upon the teacher and the students by the accountability system brings about an implicit bias against Spanish, causing the teacher to assume a paradoxical stance regarding the students' use of Spanish, and thereby, placing the students in an ambivalent position, that might affect, to a certain extent, how students use their Spanish language as a resource to participate in science learning. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]