By “discussion” activities we mean all those activities, to which a sufficiently large moment is devoted, that stimulate students to organize concepts, formulate arguments and counter-arguments by evaluating their own and others' ideas, and respond reflectively and critically to different points of view. Discussion activities involve a variety of very different modes of organization and interaction (in pairs, in groups or within the class group) and can be structured following different techniques and rules (debate, open or guided discussion, etc.).