This ethnographic case study examines a bilingual child's academic socialization in both formal and informal academic communities. The study follows a high-achieving, bilingual student in a public US elementary school, who paradoxically is seen as a slow learner in her Korean-American Sunday school. From the academic socialization and community of practice perspectives, 360 contextual, interactional, and interview events gathered from both communities over the course of one year are analyzed. The findings indicate that explicit norms and peer collaboration have a considerable effect on a child's socialization in a formal academic school context, and furthermore, that the lenient, undisciplined environment and diverse language ideologies present in an informal bilingual academic context, such as a church's Sunday school, also considerably influence a child's socialization. This paper discusses how a bilingual child constructs multilingual and multicultural competences and identities through diverse and even conflicting socialization experiences from two different learning contexts.