This article examines language classrooms as communicative settings for learners' development of sociolinguistic competence involving target language variation in a study abroad context. Specifically, it investigates how two Spanish teachers in Peru imparted knowledge of the social and contextual appropriateness of local linguistic variants that were not taught as part of the official curriculum. An analysis of ethnographic data reveals that these instructors explicitly socialized students into sociolinguistic competence through specific classroom activities intended to guide their naturalistic acquisition of Spanish away from "incorrect" forms that learners are exposed to outside the classroom. Students later reproduced their teachers' stigmatizing evaluations of these forms and described the importance of these activities for learning Spanish in homestays. These findings advance a holistic approach to research on learners' development of sociolinguistic competence as a process of language socialization that occurs both within and beyond language classrooms. Curricular reforms, teacher training, and instructional best practices are recommended that support this development without instilling the social prejudices and discriminatory practices of dominant groups from a host society.