The article analyzes meaning-making practices in a two-way dual-language (TWDL) program on the U.S.-Mexico border among "transfronterizo" and Mexican-origin youth. In the article, we show that emergent bilingual learners and their teacher participate in activities that mediate understanding of science content knowledge. We show how the teacher of a fourth-grade TWDL classroom creates a borderland space in which the full repertoire of students' languages, including translanguaging, is recognized and validated. We illustrate how the teacher, Ms. O, guides students to use strategies and meaning-making tools in both languages to construct meanings of the science content. We also demonstrate how she scaffolds students' language development, develops students' higher-order thinking, and involves all students in constructing understanding. We end with a discussion and suggestions for dual-language teaching.