The backwash effect of assessment on learning is widely acknowledged. This article discusses the impact of assessment on learning in a wider sense, by focusing on how assessment drives not only student learning, but also the teaching practices, the designing of educational programmes and the production of learning material. The focus is on how assessment affects education at a system level and the article conceptualizes the backwash effect of assessment on learning from a systemic perspective. Activity theory, as developed by Engestrom (1987), is used as a framework to conceptualize this systemic affect of assessment. The empirical basis for the analysis is an ethnographic study of the compulsory preparatory course in philosophy, logics and philosophy of science at the University of Oslo. (Contains 2 figures and 5 notes.)