At the level of the middle school, the technology is a general discipline which addresses all the pupils. So, more than ever, in 21th century, the knowledge of the world of objects is a part of the culture of the citizen. Nevertheless, the technology in middle school is a discipline still under construction, the objects of knowledge are partially defined and the research in didactics of the technology still has numerous questions to investigate. This thesis discusses the design activity of students in middle school (pupils aged 11-15) in France and particularly to designing object. At first, our purpose is to answer, in an empirical way, the following question: what are the difficulties met by the pupils in situation of design? In the exploratory way, we analyze pupils' activity resolving collectively a problem of design. We intend secondly to analyze more particularly the difficulties bound to the production of representations of the possible solutions through the role which play the computing tools of computer-aided design. It is a way to think about the integration of these tools in the teaching of the technology in middle school. Would the use of graphic intermediaries modify and in which sense the performances of the pupils of 5th in the phase of research for solutions? The recourse to the theories of the action is relevant to observe the joint activity of the teacher and the pupil and through the results which she proposes, this thesis contributes to the community of the didacticiens of the sciences and the technology.
