This paper tackles the question of factors which underpin teacher competences development; it is drawn both upon a set of research from the European project S-TEAM , and upon data collected in science classrooms. We will figure out to what extent teachers' approaches and practices with respect to inquiry based science teaching [IBST] could be altered by teacher education and training programmes or by teaching experiences. These two ways for enhancing teacher competences do exist within international expectations towards teachers. Currently, we could be concerned with a trend in many European countries, and specifically in France, which leads to maximize the role of teachers experience and so to minimize the effects of formal CPD programmes.