The article focuses on the normative conflict between quality and assessment at the basis of measures of political-educational control and methodological demands of performance. In its current accentuation, the quality of the educational system assumes the function of an extremely important prescriptive category, both for the teaching sector and for single scholastic institutions. As a specific and programmatic category, quality rests on a normative basis which, at first, is not explicated at the general conceptual level and regards the concepts of quality. The example of the national project „certification of schools for vocational training“ shows, how poor understanding of the quality concept inevitably leads to quite unspecific performance assessments, as they are controlled by implicit and immanent factors at the contextual level and thus can only provide notions of scant relevance about the most intrinsic dynamics and possible solutions.