This study explored how school librarian practices are resources that can support teaching and learning at schools in Sweden. The empirical material was produced through 22 semi-structured interviews with ‘best practice’ awarded librarians at 14 Swedish secondary and upper-secondary schools. The theoretical framework consisted of a practice theory approach coupled with analytical concepts from information infrastructure studies. The findings highlighted how teachers and librarians collaborate closely in schools with designated best practice libraries. Members of both professions collaborated in teaching and interdisciplinary projects and were supported by management teams at the schools under study. However, the librarians expressed a disconnect between themselves and the teachers and leaders of the school. This disconnect was evidenced by a lack of planning practices and classroom teaching, impelling the librarians to advocate continuously for better awareness and visibility of their practices. The article offers insights into school librarian practices at sites that function simultaneously as both workplaces for professionals with multiple competencies and educational settings for students.