For this article we aimed to understand the emergence of English as a second language for a newly immigrated Mexican student, a native speaker of Spanish, enrolled in a mainstream kindergarten classroom, who was undergoing the "silent period" (Krashen, 1981). Applying ecological approaches that emphasize learners in relationship with their environment, we analyzed three particular classroom practices and their respective mediational roles for the development of a second language (L2). Following Tomasello's (1999, 2003) recognition that the understanding of communicative intentions is an essential prerequisite for language development, we argue that certain characteristics of routine classroom practices (i.e., shared objects, infrastructural elements, and speech patterns) provided key interactional and contextual affordances for the understanding and internalization of a shared system of symbols (linguistic and nonlinguistic) and, thus, for the emergence of the L2. This research suggests that our focal student was intentionally and actively engaged in L2 learning during this period of silence. In addition, our findings suggest that although the understanding of communicative intentions contributed to the legitimization of a "student" identity for the learner during the silent period, it did not contribute to the learning of academic content. We argue that ambiguity and multiplicity of intentions conveyed in some classroom actions may be particularly challenging for L2 learners in mainstream classrooms. (Contains 1 figure and 5 footnotes.)