The idea that schools, as social institutions, operate between the two poles of promoting and selecting is part of the established knowledge corpus of educational sociology and school research. This structurally functionalist perspective has long permeated everyday theories and can also be found in writings for teacher training and professional development. The school - this is the view - not only has the educational mandate to promote each student individually, but it is also committed to the principle of selection. As straightforward and simple as this dual task may seem, the controversies surrounding the concepts of promoting and selecting, as well as the political ideas associated with them, have sparked intense public debate. As the history of education policy clearly shows, discussions about the design of the education system, particularly regarding primary schools, repeatedly revolve around the question of whether enough and appropriate promotion is taking place or whether there is enough, or perhaps too much, and appropriate selection. The debates sparked by the spirit of change in the 1960s and 1970s were fueled by the irritation that school practices contradicted the self-understanding of modern society, which holds that all people have the same educational opportunities and that social inequality is reduced through education.