A hundred days before high school graduation ( the “baccalauréat”), the ending students are dressing up and going in the street to collect money, then they are taking lunch together to finally join on the evening to dance and enjoy themselves. We shall evoke the case of “Père cent” celebration stemming from very old and popular customs. Its sociological study allows to show that it contributes to mark the transition from childhood to adulthood. I put forward that this celebration introduce a real rite of passage in which that feast assumes the preliminaries’ post according to Arnold van Gennep’s theory. Nothing is officially instituted, we are in the framework of social behaviour moved by a collective imagination. The “baccalauréat” is, at the same time, the revealing and the telltale sign of that celebration and an opportunity to shape that rite of passage.