This study examines the social construction of proficiency and the discursive practices prevalent in linguistically diverse schools that afford or constrain participation in language learning communities. Drawing from discourse studies, positioning theory and a sociocultural framework, this study analyzed data from audio recordings and ethnographic observations of a fifth grade dual-immersion classroom. Analysis of moment-to-moment interactions and the construction of classroom language norms throughout the school year shed light on the ways that students and teachers work together to enact perceived proficiencies and position learners as (non)participants across different school contexts. Findings suggest that educators can orchestrate learning contexts that re-position students as proficient language users and sources of language expertise. This study contributes to research in educational linguistics by making the case for "perceived proficiency" as a construct to make visible the ways that language proficiencies are reified and shifted throughout interactions with others. (Contains 1 figure.)