Peer assessment (PA), as formative procedure, enhances learning by providing students with the opportunity to peer assess each other's work. However, since students exhibit different value systems (abilities, experiences, attitudes, cognitive styles, etc.) we propose a diagnostic procedure, which can be applied at the beginning of a course, in order to infer the most prevailing attitude among students. For this purpose, the proposed methodological framework, based on a multi-criteria clustering approach, identifies different assessment behaviours, in order to adopt the most common student assessment policy. To demonstrate the proposed method, an example is presented where two different PA data-sets are examined. The results clearly indicate that students exhibit different PA policies, nevertheless, a densely populated group is formed, the value system of which can be adopted thereafter.