By implementing strategies such as the Lisbon Agenda (2000 - 2010) and Europe 2020 (2010-2020), the European Union explicitly puts science education at the heart of economical development, and stresses scientific excellence as a means to economic growth. In this context, France has aimed to revalorize its science courses and careers in order to make them more attractive and to foster greater inclusion and diversity. Women, and students from the working classes or ethnic minorities are indeed particularly marginalized in science, especially in France where social equity is far below OECD average and has been degrading between 2003 and 2016 (OECD, 2015) One of the way to translate the European initiative and to try to reduce the gap between students has been to promote and support partnerships between schools and the scientific world. This paper accounts for one of those cooperations in order to analyze what goes on in classrooms when two different cultural groups — teachers and science mediators — work collaboratively. It provides insight into the reasons for success or failure of such practices and asks how and why difficulties emerge in this type of partnership. We argue that partnerships between secondary school teachers and external specialists create unusual teaching situations that upset their roles in the classroom.The purpose of this paper is to offer a sociological analysis of conflicting relations between teachers and science mediators through the case study of a French collaborative science project in 6th grade (11 and 12-years-old students). An ethnographic approach allows us to render the conflict’s expression in the classroom and the justifications provided by the partners. This study uses a Bourdieusian framework by proceeding to an objectivating distanciation in order to give meaning to the plurality of judgments in the field created by the collaboration. The qualitative analysis, conducted by observations and interviews, aims to enlighten the contributors’ social positions and the partnership’s challenges. Methodology, Methods, Research Instruments or Sources Used This study consists in the qualitative analysis of a partnership in science education through observations and interviews. We observed weekly science workshops during three years — 4th to 6th grade; this paper touches on the last year — and took detailed notes on interactions between teachers, mediators and students. We also had the opportunity to attend preparatory and review meetings for the workshops, where teachers and mediators set up and assessed their collaboration. Later on, individual semi-structured interviews were conducted with the science teachers and the mediators who had taken part in the program. Explored themes included careers, personal attitudes to science, and perception and assessment of the program. We also conducted interviews with about 50 students, but this material will only be treated as a secondary source for this paper which focuses on adult interactions. The empirical material thus recovered is analyzed through Bourdieusian perspective in order to bring out and explain contradictory behaviors and perspectives amongst the stakeholders. We also draw upon the concept of “bicephalous didactic system” (Loquet, Garnier et Amade-Escot, 2002)  in order to theorize a “bicephalous pedagogical system”, enabling us to better understand what goes on in the classroom during such collaborations. Conclusions, Expected Outcomes or Findings After reporting on the history of the partnership and on its conflicting evolution, we justify this unfolding by explaining how pedagogics, and not didactics, are at the heart of the collaboration, since practices are made independent of the content of the knowledge to be transmitted. In the case described here, we argue that an implicit inversion of the partners’ roles and an unspoken competition between two different teaching approaches (active pedagogy for the mediators; transmissive pedagogy for the teachers) causes the conflict and precludes collaboration. We detail the evidence of this inversion and compare it with educational texts that should govern partnerships, and with intended forms of collaborations. Finally, we wish to provide elements of generalization regarding educational partnerships by questioning the links between French educational specificities and European directives as well as the role that researchers can play in this type of program. References Astolfi, J.-P., Develay, M. (eds.), 2002,  La didactique des sciences (Science didactics), Paris, Presses Universitaires de France. Becker H., 1998, Tricks of the Trade, Chicago, The University of Chicago Press. Bourdieu P., 1997, Les usages sociaux de la science : Pour une sociologie clinique du champ (The social uses of science: For a clinical sociology of the field), Paris, INRA. Bourdieu P., 2001, Science de la science et réflexivité (Science of science and reflexivity), Raisons d’agir, Paris, Raisons d’agir. Devos-Prieur O., Loubet-Gauthier É., 2002, « L’incidence des modes de partenariat à l’école élémentaire sur la polyvalence des maîtres et sur les représentations des élèves du travail scolaire. 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