Recently, "Team School" (School as a Team) has been proposed as a new image of schools in Japanese educational reform. Team School is an organizational model where teachers and non-teaching professionals (e.g., school counselors and school social workers) collaborate in order to respond to the increasingly complex and diverse issues the school faces. Considering the long history of Japanese schools where teachers alone manage all educational activities for students, this new school model based on more involvement of non-teaching professionals seems necessary for the school to expand support for diverse students as well as to keep education sustainable. However, there are several issues for the progress of Team School, such as the lack of new professionals and the existing teachers' workstyle. In this article, the author focuses on school-based collaboration for student support as an aspect of Team School and examines the issues for its implementation. To clarify these issues in Japan, the author examines the case of "Safeguarding Teams" in UK schools. Also, findings from the author's field research at a Japanese junior high school are used to examine how to realize Team School and improve collaborative support for students.