Functional analysis of the relation between knowledge and education system from the viewpoint of quality is used in the paper. It is proved that it is not necessarily true that there is a correspondence between knowledge quality and construction of the education system, i.e. that the former quality is not an inevitable condition of the latter. In the first part of the paper, we distinguish the concept of quality from non-quality knowledge. Out of 19 indicators, five knowledge qualities are normative (exceptional sense), and the others descriptive (specific sense) characteristics. In the second part, the conceptual approach to education system focuses on its (dys)functional and non-functional connections. The tradition of national knowledge, the character of social relations established between the actors within the system and the influence of implicit knowledge on teacher and student actions in education system are discussed. All these factors can influence positively and negatively the direction and content of knowledge quality in education system. Knowledge quality in school curricula and textbooks may be ensured and then (not) realized due to the influence of traditional, social and implicit factors on educational interaction. The concept of constellation is used to explain the favorable and unfavorable relation between knowledge quality and education system. In the concluding part, the author argues that education system cannot ensure complete realization of knowledge quality since it is, to a considerable extent, conditioned by school and non-school factors.