ABSTRACT
Teacher knowledge may have a variety of origins, including formal schooling in the past, that is, initial disciplinary training and teacher education, or continued professional training (cf. Calderhead, 1996), as well as practical experiences, occurring in day-to-day teaching practice. In this sense, teacher knowledge is not opposite to theoretical or academic knowledge. Obviously, teachers may differ enormously in the extent to which they have merged or integrated knowledge from different sources into conceptual frameworks that guide their actions in practice.
