This article considers how historians might use imagery in the context of an open-air school in Germany, Senne I-Bielefeld (1922-1939). In considering the "nature" of such images, issues and problems associated with their interpretation are illuminated and discussed. First, two images selected from the pre-Nazi period of the school are examined within a theoretical discussion. Then, the article explores the question of how historians might understand the "discipline" of the body of the schoolchild through its representation in photographs. The open-air school is thereby considered as a demonstration of the result and possibility of bio-power. Through such visual representations an argument is developed to reveal the meaning of the body in the school with reference to children's experience of the school's power/knowledge. A third image from the Nazi period of the school is employed to point to changes in the representation of children's bodies over time. Finally a plea is made for more attention to the emotional engagement of the historian as a valuable source in the history of education. (Contains 3 figures and 111 footnotes.)