Reforms made to France's education system structures during the 1960s resulted in a repositioning of academic subjects within study plans. This article looks at three relatively similar subjects (physical sciences, natural sciences and physical education) and throws light on the arguments put forward to defend the purpose of each of them in the educational process. The arguments provided intended not only to establish each subject's legitimacy from mainly economic, social and political points of view, where the aim was to form the future leaders of a modern society, but also from the academic perspective. Indeed, each subject had to position itself within a changed "hierarchy", giving rise to new interdisciplinary issues which contributed to the transformation of French schools. (Contains 1 table and 2 notes.)