1 Tiberghien, A. (2000). Designing teaching situations in the secondary school.. In R. Millar, J. Leach and J. Osborne (Editors): Improving science education: the contribution of research. Buckingham, UK: Open University Press. pp. 27-47 Towards Research-Based Design of Teaching Situations In Physics at the Secondary School Level Andrée Tiberghien Université Lyon 2; GRIC équipe COAST France The relationship between research in science education and effective teaching in the framework of any educational system raises the question of the role of research in designing teaching situations. This design for each domain of physics can be an endless task. In this chapter I present an approach to designing situations based on teaching and learning where the knowledge to be taught, students' understandings of that knowledge and teaching resources are each viewed as important, and with the potential to influence each other. The theoretical bases of such designs are first presented and then three types of situations are analysed. THEORETICAL BASES The theoretical elaboration presented here has been developed following a series of empirical studies carried out in the COAST research group (France), with data mainly collected in classrooms during practical work at the upper secondary school level (Bécu- Robinault, 1997a, b, Buty, 1998, Le Maréchal, 1998); it is also rooted in a collaboration with teachers (Gadioz et al. 1998). The results obtained, together with theoretical approaches on modelling (Tiberghien, 1994), on didactical situations (Brousseau, 1988), and on didactical transposition (Chevallard, 1991) constitute the main bases of this research-based design of physics teaching situations. Knowledge First of all, it is necessary to note that in English, the single word ‘knowledge’ is the only one available, whereas in French there are two words: savoir(s) and connaissance(s), with the associated verbs. This makes it difficult to present in English the theoretical framework constructed in the French language. Due to the international character of this book, this remark can help mutual understanding. The theoretical position on knowledge is based on Chevallard's work (1991) — a French researcher in didactics of mathematics — who, to deal with knowledge, uses the metaphor of life and ecology. Knowledge "lives" within a group of people called an