This study focuses on the discourse characteristics of Latino children's and teacher interactions during science instruction. Peer interaction was analyzed to describe the use and importance of the native language (L1) for the development of content knowledge and literacy skills in Spanish. In addition, the interaction between teacher and children was analyzed to determine the importance of adult's use of L1 in providing instructional support in L1 to make science and literacy meaningful for linguistically minority students. Over the course of one semester, classroom observations focused on how a Spanish-English bilingual teacher approached the demands of science inquiry in an urban 4th grade classroom in northern California. The results for classroom observations included two types of data. One is based on the qualitative field notes made during weekly classroom observations where teacher and children participated, and the other is based on a discourse analysis of children's speech acts while they participated and completed a Science activity. Children's conversations were deployed with different discourse strategies to accomplish their communicative goals during the Science activity. While Spanish was used mainly as the language of instruction during the Science activity, children used code-switching in Spanish and English to challenge each other, reinforce major science concepts, and to develop biliteracy skills. The discourse strategies for promoting academic achievement using native language and second language instruction with Spanish-English bilingual children are discussed in this presentation.