Based on the challenges that the francophone Association for Comparative Research in Didactics faces since its creation in 2006, this paper positions “comparative didactics” (didactique comparée) as a reconstructive move drawing on certain conceptual frameworks developed in the earlier “subject didactics” and against the background of socio-cultural approaches of knowledge construction and learning. The aim is to provide a better understanding of the three-fold relation [teacher - student(s) – content] across the various forms of institutional contexts in which teaching and learning is purposively organised and across the frontiers of the school subjects. Comparative didactics certainly strives towards the elaboration of fundamental models for theorizing “the didactics” (a social fact as a whole, as Chevallard put it) but we argue that such an elaboration is necessarily rooted 1) in the empirical investigation of the knowledge-specific teaching and learning practices, including both a situated and socio-historical approach and 2) in the epistemological investigation of the concepts construed in subject didactics, as a means to delineate the potential compatibility among them. In this perspective, the paper will examine some potentials and limits of the Joint Action Theory in Didactics as developed by G. Sensevy’s recent works to meet the purposes of comparative didactics.