Educational phenomena and child development fascinate many disciplines for which they offer a tremendous field of experimentation and application. More than a hundred years ago, when educational sciences adopted the main institutional emblems of an academic discipline (chairs, diploma, laboratories, scientific network etc.), they obviously vacillated between the dream of becoming a unified science (as pedology testifies), and the claim of a rewarding pluridisciplinarity that could synergise all disciplines concerned with the child and with education. This paper asserts that the issue of pluridisciplinarity is constitutive for the development of sciences of education whose object is ever coveted by other disciplines. The first section adopts the point of view of a social history and, on the basis of voluminous archives, it describes the main lines of the shaping of this pluridisciplinary field in Geneva, representative of that which also occurs elsewhere. In the second part, it presents a more theoretical reflection on the tensions and pitfalls of what we call the "process of disciplinarisation" of educational sciences, outlining the characteristics of this constitutively pluridisciplinary field. (Contains 5 notes.)