A Vygotskian approach to assessment is proposed by invoking the distinction between the development of lower and higher psychological functions. Higher psychological functions are specifically human and develop with the use of cultural tools via mediation. Accordingly, a distinction is made between tests that are based on association, which have lower psychological processes as their object of measurement and tests based on mediation that target higher psychological processes. Within a Vygotskian framework of human development, the goal of effective education (i.e., teaching and learning in formal contexts) is developing higher psychological functions. Therefore, assessment, whose purpose is to assess the outcomes of educational processes, should be capable of gathering evidence of the development of higher psychological functions.