First-grade students often come to school relatively naive about what it means to be mathematics students. Thus, first-grade teachers have the responsibility not only of teaching mathematical content to their young students, but also of socializing them into a culture of mathematics learning. In this article, the authors document both how teachers provide explicit instruction about participating in mathematics learning and how they implicitly communicate to young students what counts as appropriate behaviors for engaging in mathematics learning. The authors also discuss how these instructions and practices lay the foundation for students' understanding of how they are expected to engage in learning mathematics.