This paper presents the results of a field experiment, in which a variation in the didactical arrangement of a training course for teachers was investigated. It was hypothesized that a conceptually oriented training program, consisting of certain training components, would benefit teachers most. The theoretical background of the hypothesis is discussed. The impact of the variation on teachers' knowledge, perception of competence and performance was assessed. The results show clear support for the hypothesis on measures related to knowledge and perception of competence, but not on those related to performance or actual competence.