In a Europe traumatized by the First World War, educationalists point the finger of blame: the school, which produced “brave soldiers”. The task now is to build peace and develop a new education for a generation of children who, it is hoped, will never wage war again. How can we educate them without surveillance and punishment? How can we help them to emancipate themselves? To make children happy is to make them better adults, according to those who embarked on the adventure. Their names are Rudolf Steiner, Maria Montessori, Célestin Freinet, Alexander S. Neill, Ovide Decroly, Paul Geheeb or Janusz Korczak, each of them inventing educational methods. A Swiss pedagogue, Adolphe Ferrière, brought them together in the Ligue internationale de l'éducation nouvelle.