The international PISA student assessments presently function as the central framing for the development of educational systems across large parts of the Western world. The goal is comparisons of the competencies of students across countries to make differences betweenthe effectiveness of educational systems clear. This paper will question some of the epistemological assumptions in PISA. Drawing particularly on Polanyi’s concept of tacit knowledge, we argue that PISA represents a partial and limited view on knowledge being individualistic,verbal, and unambiguous. In opposition to this, we argue that knowledge for Polanyi is a much broader phenomenon where the body, tools and tradition are key components. Furthermore,we argue that Polanyi’s concept of knowledge is useful to approach the complex issues that the educational system faces today.