Focus is shifting from individualized to collective learning for teachers, but many schools struggle to structure and enhance collective professional learning. This interview study aims to explore possibilities for and barriers to leading collective professional learning in school by studying teachers' and principals' perspectives on how school leaders facilitate and monitor teachers' collective professional learning. The data include group interviews with teachers and individual interviews of principals from two schools who participated in an initiative to develop lower-secondary schools in Norway. We find a difference between school leaders' intentions and their enactment as reflected in teachers' experiences, revealing the complexity of leading collective professional learning in school and transforming leadership theory into practice. We argue that the potential to facilitate collective professional learning among teachers emerges when leaders set and incorporate a collective direction, systematically follow-up and adapt collective learning processes over time, and include systems thinking and sensitivity toward the school context. Furthermore, a transparent and collectively oriented implementation plan can better involve teachers when planning and adapting the collective direction and learning processes. Teachers' and principals' diverse experiences contribute to expanding our understanding of how to lead collective professional learning among teachers.