The purpose of this study is to describe, analyse and evaluate the successive comprehensive reforms in Spain as a "paradigmatic" example of the emergence, evolution and crisis of the comprehensive school. In the first part, we describe the development of the comprehensive school project (1970-2013), using the image of the life cycle, with its corresponding turning points. The second part consists of a diachronic and "retrospective critical review" of why a progressive educational reform like the one passed in 1990, which was intended to be comprehensive, has paradoxically led to high rates of academic failure and early school leaving. What factors managed to undermine the proposal, leading to the current return to less inclusive solutions? From the perspective of a certain change in cycle, a more objective view is possible.