The article deals with a particular aspect of the competencies-based approach in the curricula of basic and secondary education: the role of complex situations in learning. What should their role be so that education systems gain both in effectiveness and equity? Many research outcomes have shown that it is important to stress first and foremost complex ''post'' situations in learning knowledge, know-how and life-skills. It is a matter of complex situations (integrative pedagogy) in which the pupil is invited to use the knowledge, know-how and life-skills already acquired, not as ends in themselves, but as resources that the pupils employ to confront the complexity of their environment. It shows to what extent using the problem-solving approach to inculcate knowledge and know-how, in other words using complex situations for ''prior'' learning, represents a less suitable innovation. Professor of educational sciences at the Catholic University of Louvain-la-Neuve and director of BIEF. A civil engineer, primary school-teacher and doctor of educational sciences, he specialises in curriculum development, evaluating student achievement, designing and evaluating textbooks, teacher training and equity in education systems. Together with his team, he is currently providing support to the education systems in some 30 countries North and South, and collaborates with the major international organizations, such as OIF, UNICEF and UNESCO. He has authored numerous works on the competencies-based approach, including, most recently, Une pédagogie de l'intégration and Des manuels scolaires pour apprendre.