This contribution concerns the teaching and learning of duality in linear algebra. Combining an institutional, and a didactic contract perspective we argue that some of the novice students' difficulties can result from specific features of the university contract, at different levels. Analyzing university textbooks, we identify such features, in the case of duality. Drawing on these observations, we design an experimental teaching, aiming to support the students' entrance in the new contract, at different levels. We investigate the impact of this experimental teaching. Analyzing students' productions, we observe that they developed abilities specific from the university contract, concerning duality or more generally mathematics.