Since the late 1980s, support to agriculture has moved from top-down agricultural extension towards more participatory approaches which better suit smallholder farmers. One such approach is the farmer field school (FFS), an adult education intervention which uses intensive discovery-based learning to promote skills. Although FFS has been used to train 12 million farmers in over 90 countries across Asia, Africa and Latin America, the effectiveness of this approach has long been a subject of debate.