The article propose a new way of looking at the relationship between content elaboration and formulation during the production of written argumentative texts. It is hypothesized, that younger students elaborate contents by formulating them, whereas in older students both processes are clearly distinguished. 8 pairs of students aged 10 and 14 and adults with academic background produce a text in a collaborative situation. Three aspects of the production of the first and the last sentence are analyzed in looking at the (...) recorded dialogues: elaboration of argumentative plans; the independant elaboration of contents; the variation of linguistic forms. The results gives the hypothesis credit and show a deep reorganisation of the production process of argumentative texts in ontogenesis. (shrink)