This paper presents the findings of a 2023 research conducted by the co-research committee of Hiroshima University in collaboration with Hiroshima University Schools. The study focuses on the development and implementation of a boundary-crossing curriculum aimed at fostering teachers and students/children as active agents in their learning journey. Through an analysis of praxis and research reports from 11 Hiroshima University Schools, the study investigates the concept of “boundary-crossing” and its implications for educational practice. The paper then deliberates on the significance of the “boundary-crossing” curriculum, emphasizing its pedagogical value in facilitating collaboration between schools, subjects, and grade levels. The paper also underscores the need for further pedagogical inquiry into the impact of boundary crossings on students and children.