This paper reports on how teachers, from different cities in Brazil, used groups on Facebook and how communication between teachers and students was affected by using such groups. This study is framed under the Cultural Historical Activity Theory (CHAT) perspective, and is conceived from a methodological background that invites participants to collaborate during the research. We examined posts from the groups on Facebook from February 2013 to June 2014 by a qualitative approach, together with coding the open-ended qualitative data and comparing their distribution, and analyzed responses to a questionnaire for teachers by the end of the research. Our findings suggest the teachers used the groups for different purposes, which led to an improvement in communication between teachers and students--online and in-classroom--and in students' engagement in the classrooms.