Student-teacher relationships are vital to successful learning and teaching. Today, communication between students and teachers, a major component through which these relationships are facilitated, is taking place via social networking sites (SNS). In this study, we examined the associations between student-teacher relationship and student-teacher Facebook-mediated communication. The study included Israeli middle- and high-school students, ages 12-19 years old (n=667). Student-teacher relationships were compared between sub-groups of students, based on their type of Facebook connection to their teachers (or the lack of such a connection); their attitudes towards a policy that prohibits Facebook connection with teachers; and their perceptions of using Facebook for learning. Regarding students' attitudes towards banning student-teacher communication via SNS and towards using Facebook for learning, we found significant differences between three groups of students: those who do not want to connect with their teachers on Facebook, those who are connected with a teacher of theirs on Facebook, and those who are not connected with a teacher of theirs but wish to connect. Also, we found significant associations between student-teacher relationship and student-teacher Facebook-mediated communication. We argue that in the case of student-teacher Facebook-mediated communication, there is a gap between students' expectations and in-practice experience. The key to closing this gap lies in both policy and effective implementation.