The United States is a multilingual society. In addition to over 200 named languages such as Spanish and English, Americans also speak hundreds of varieties of these languages based on regional or social group affiliations (United States Census, 2013). In the context of this linguistic diversity, education scholars and practitioners are working towards promoting deeper learning, improving educator quality, and providing equitable access to educational resources and opportunity (Learning Policy Institute, 2019). For science education in particular, where traditionally, instruction has focused on content coverage and fact-memorization (Schwab, 1958; Duschl, 1990), educators are faced with the challenge of how to provide rich learning opportunities based on discourse and engagement with scientific practices within linguistically diverse communities ( Lee, Llosa, Grapin, Haas, & Goggins, 2019; Lee, Miller & Januszyk, 2014; National Research Council, 2012). While science education research has explored literacy, discourse, and emergent bilingual students, the issues surrounding monolingual science teachers working within multilingual communities is still largely uncharted territory. Calls for attention to issues of equity in education span decades, and have been increasing in recent years (Cohen & Lotan, 2014; Darling-Hammond, 1997, 2005), and many scholars have draw attention specifically to equity issues related to multilingual science students (Lee, Miller, & Januszyk, 2014; Quinn, Lee, & Valdes, 2012) . Particularly, science teachers' approaches and ideologies towards multilingualism remains understudied, as are the ways in which those approaches might influence educational opportunities for multilingual students. Asset-based perspectives on learners seek to subvert deficit views of multilingualism (Garcia & Guerra, 2004), but little is known about whether these perspectives exist among science teachers and how they might influence science teaching and learning.Study I in this dissertation identifies how science teachers move between inclusive and exclusive approaches towards language--both promoting monolingual norms that inadvertently marginalize the multilingual resources of their students as well as subtly welcoming multiple modes of communication in science. Study II looks at the results of shifting towards an asset-based approach to linguistic diversity by investigating how different ideologies, when communicated by the introduction to language-diversity, can shape the scientific discourse of students working in small groups. Its findings showed that students who were given a task introduction aligned with an asset-based approach made more evidence-based claims and offered more critiques of each other's ideas in comparison to a group given a more science-focused introduction. The impact of an asset-based introduction to multilingualism was quantitatively demonstrated by the results of the final study. It revealed that introducing a positive stance towards language diversity led students to have more optimistic beliefs about their ability to overcome obstacles and to use science to solve problems. In sum, the studies conducted in the course of this research offered evidence of the value of shifting classroom practice in science classrooms to an asset-based approach that views multilingualism as a benefit and allows for translanguaging in the classroom. Together, these studies provide evidence about how a group of science teachers view language diversity and multilingualism as well as how an asset-based approach to multilingualism influences science students. [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://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]