This article is grounded in the process-mediating paradigm according to which the pupils’ perception of the classroom environment is more influential for the pupil’s school adaptation than the objective features of this environment. In the case of pupil assessment, it means that the perception by the pupils of the teacher’s conception of the goal and use of assessment can be supposed more important than what the teacher thinks really about that. In this perspective, we develop questionnaires aimed to measure separately the conceptions of teacher and these ones of pupils (at the end of primary school) in regards of the functions of pupil assessment. We also created a questionnaire for capturing the pupils’ perceptions of the teacher’s conceptions in regard to assessment. At first, we validated the three questionnaires (alpha of Cronbach, exploratory and confirmatory factorial analysis). Then, we analyze the relationships between these parameters. It appears that teachers and pupils have a multidimensional conception of pupils’ assessment. Moreover the conceptions of teachers and pupils are highly convergent. However, in the classrooms, the conceptions of the pupils do not fit with these ones of the teacher and, moreover, the pupils perceptions of their teacher’s conceptions concerning assessment do not correspond to what teachers declare as their own conceptions. Pupils’ perceptions of their teacher’s concept ions in reality correlate highly with their own conceptions concerning assess ment. Pedagogical implications of these findings are discussed at the end of the paper.