Transformation of didactic intentions by teachers: the case of geometrical optics in grade 8

This investigation is based on the following idea: as regards the implementation of research based innovations, teachers are not passive transmitters, and some general trends can be found in the way they transform the proposed strategies. This paper deals with the particular case of elementary optics in grade 8 in France, a syllabus launched at national level in 1993. Four sets of data - interviews before teaching, logbooks, assessment tasks and video recorded class observations lead to converging conclusions. These suggest the interest of extending such research to other topics and provide some hints on how to design innovations with maximized chances of appropriate implementation by teachers.