Research on linguistically and culturally sustaining science education has recently placed increased attention on the need to rethink the field by promoting more equitable pedagogical opportunities for all students. In this dissertation, I explored and analyzed different contexts where language and science were used to promote emergent bilingual learners as agentive meaning-makers within the NSF-funded Language-rich Inquiry Science with English Language through Biotechnology project. To this end, I inquired into two contexts of language production and meaning-making. First, I focused on the classroom practices of a LISELL-B trained educator working with bilingual newcomer refugee learners. Second, I analyzed the linguistic production of Hispanic students in constructed-response assessments. Drawing on the theoretical lenses of Systemic Functional Linguistics (SFL) and Culturally Sustaining Systemic Functional Linguistics (CSSFL), this dissertation also provides insights on the role of language as a fundamental means for human transformation.Presented as three article-length manuscripts, the central purpose of this dissertation was to analyze contexts of enactment in which teachers and students became agentive meaning-makers. In the first manuscript, I address how Teacher Professional Learning (TPL) can function as a powerful resource in supporting culturally sustaining educational practices for multicultural and multilingual students. In the second manuscript, I investigate the classroom practices of a bilingual science teacher in the context of a program for newcomer bilingual students. In the third manuscript, I argue that the field of science assessment needs to rethink and reflect not only on how scores are generated on assessments but also on what analyses are done with such assessments to inform teacher instructional decisions. Findings from this dissertation are aimed at contributing to the science education of bilingual Latino students within and beyond the U.S. context.