Research focused on learning mathematics in a 2nd language is generally located in individual 2nd-language contexts. In this ethnographic study, I investigated mathematics learning in 4 different second-language contexts: a mainstream classroom, a sheltered classroom for Indigenous students, a welcome class for new immigrants, and a French-immersion classroom. The study was framed by a view of learning as socialization and the Bakhtinian notion of centripetal and centrifugal language forces. I present 7 socialization events that were particularly salient in 1 or more of the classrooms. For each socialization event, I identify various socialization practices. Based on a comparison of socialization practices in the 4 classrooms, I propose a distinction between language positive and language neutral mathematics classrooms. In language positive mathematics classrooms, students' socialization into mathematics and language includes explicit attention to different aspects of language use in mathematics. In language neutral mathematics classrooms, the role of language in mathematics tends to be implicit.