The present project aims at evaluating the impact of inquiry-based science teaching methodology training for primary school teachers on educational methods and pupil scientific competencies. Numerous papers confirm the advantages of such educational methods. But these results generally rest on small sample studies or may be linked to very specific frameworks. Our project aims at evaluating the impact of such training in a large scale, real institutional, thus ecological, context (160 trained teachers). Our methodology is based on a randomized control trial linked with a very detailed qualitative approach. The projet will evaluate training sessions organized by «Maisons pour la Science» recently created by the «Main à la Pâte» foundation. The sessions will last 80 hours and will be operational in September 2014. The questions that we wish to address are the following : a) which impact on educational practices of trained teachers ? b) which are the most effective levers to make real change towards inquiry-based educational methods ? c) which impact on knowledge, competencies and science behaviour of trained teachers' students? The project will benefit from the assets of two complementary approaches : - a rigorous statistical approach, comparing randomly selected treated and control teachers. 160 teachers will be trained and 160 will be in a control group. The control group will follow a short training on identical topic. This ensures that impact evaluation is not biased by endogenous teacher selection into treatment. - a qualitative approach that will be based on a very detailed observation of « Maisons pour la science » training sessionss and teacher practices. We will observe changes in educational methods using video recordings of teaching sequences inside classrooms. It will also help build the quantitative questionaires used in the statistical analysis. The general objective is to analyze not only a teaching method, but the full social chain that goes from teacher training to actual practice and student outcomes. This project will be led by a pluri-disciplinary team of experts in education economics and social experiments, science didactics, cognitive science, teacher training. The project will attempt to bring robust evidence in an international context where many countries want to reform their initial educational system relying on evidence-based policies.