For over two decades, US bilingual education has been underdeveloped and underexplored due to the No Child Left Behind policy. Thus, additive bilingual-education programs, which develop students’ primary language while simultaneously adding a second language (L2), are becoming more popular in K-12 schools. Traditionally, L2 theories and education tend to focus on narrow aspects of language learning, e.g., vocabulary, grammar, and skills in listening and communication. Students have rare opportunities to contextualize language or participate more deeply in an L2. This work considers a contextualized approach to bilingual education, an integrative model of critical biliteracies (Cope & Kalantzis, 2015; Luke & Freebody, 1997;), which considers dynamic identity making as part of language learning. This approach combines critical literacy pedagogies with a multimodal approach to language teaching to support students in learning how to interpret, critique, and produce writing by taking advantage of writing, speech, visual and tactile representations, in both their home language and L2. I examine the intersections between L2 acquisition, specifically writing and writing processes, and dynamic identity making for fifth-grade students in a bilingual elementary school in New England, where I conducted ethnographic research through critical sociocultural perspectives that allowed me to understand how language and literacy learning work with power relationships and produce student identities. Specifically, I consider students’ “becoming” and how an immersive language-learning environment develops transcultural and transnational student identities. My research, whose design is based on critical ethnographic case study, investigates the cultures of a fifth-grade classroom during one school year. My results could subvert mainstream assumptions about L2 acquisition by examining whether fostering dynamic identities for L2 learners is crucial to becoming bilingual and biliterate. My findings challenge the linear perspective of language learning, i.e., the idea that language acquisition need not impact students’ core identities, by questioning whether accepting and fostering students’ dynamic identities facilitates their attaining fluency in the L2. My results address a glaring research gap by offering educators an alternative way to support L2 learners as they interact with the wider world. The findings should greatly interest L2 educators, researchers, and curriculum specialists, by offering a new pedagogical approach to language and literacy learning, one that combines applied linguistics with a critical attention to sociocultural dynamics.