How teachers and students deal with assessment practices is largely influenced by the conceptions they hold about the purpose of assessment. This means that, given the current plea for a paradigm shift from assessment of learning to assessment for leaning with a balance between the formative and summative purposes of assessment, the study of teachers’ and students’ conceptions of the purpose of assessment is of the utmost relevance. In this study dutch secondary school teachers’ (n = 351) and students’ (n = 712) conceptions of the purpose of assessment were measured using a translation of the teachers’ conceptions of assessment questionnaire and a translated and shortened version of the students’ conceptions of assessment questionnaire. Maximum likelihood factor analyses resulted in four teacher and five student conceptions of the purpose of assessment. The results indicate that the teachers in our sample did not distinguish between formative and summative purposes of assessment. They did discern classroom assessment (formative as well as summative) from school accountability. In addition, they conceive assessment as being of bad (in terms of measurement errors) or good quality. In contrast with the teachers, students do make a distinction between the formative and summative purpose of assessment. They also refer to school accountability and the affects that assessment triggers in them as further purposes of assessment.