Background: A wide variety of information and communication technologies (ICTs) is increasingly embedded into numerous facets of everyday life. Young people, in particular, are often viewed as eager and skilful users of new ICTs who have various educational and leisure-related purposes for ICT use. Although school and home lives have traditionally been viewed as separate, ICT use has blurred the lines between these environments. This study focuses attention on the negotiation of this 'grey zone' within the school setting, in terms of teachers' practices around students' online interactions. Purpose: This study sought to gain insight into teachers' perceptions of the challenges related to students' online interactions and how these become visible in the school context. This included exploring strategies identified by teachers in efforts to surmount difficulties. Methods: Data collection involved semi-structured interviews with 15 teachers in Finland working in primary and/or lower secondary education. The transcribed data were analysed qualitatively, using a thematic approach. Findings: According to the teachers, there were significant challenges associated with young people's online interactions that affected their students and the flow of school life, such as online conflicts and dysfunctional behaviour in messaging groups. Although teachers found that the boundaries and the obscurity of their roles made it difficult to address some situations, they nonetheless identified strategies to overcome challenges, often including collaboration with students and parents. Conclusions: The study highlights how students' online interactions can affect the ways that teachers view themselves and their roles as educators. Given the pace with which ICT, and young people's use of it evolves, the study suggests that there is a need for frequently reviewed guidelines or practices that help clarify the roles of different actors in relation to the realities of students' ICT use.