This paper is a part of a larger research project, which focused on investigating the teacher development practices in a Languages without Borders community of a large university in the south of Brazil. The research is affiliated with the paradigm of Practice Theory (Young, 2009; Young, 2010) and relied on qualitative methods of data generation and analysis (Erickson, 1990; Gumperz, 2005; Mason, 2002; Tannen, 2014), as well as on semistructured interviews with focal participants. The data revealed that the practices that culminate in teacher development could be divided into two: (1) formal practices, that is, the ones consciously planned and carried out by the coordinator; and (2) informal ones, that is, practices that emerged from everyday life in this community of practice, chiefly in the teachers' room. In this paper, we focus on a specific informal practice - that of planning classes together. Planning classes together was considered a productive practice in terms of professional learning both in the interviews and in the data obtained through participant observation.