This paper addresses how teachers can be trained to enable cumulative knowledge-building. It focuses on the final intervention stage of the "Disciplinarity, Knowledge and Schooling" ("DISKS") project at the University of Sydney. In this special issue, Maton identifies "semantic waves" as a crucial characteristic of teaching for cumulative knowledge-building; and Martin explores a "power trio" of intertwining linguistic resources which contribute to the creation of these waves. This paper draws on these complementary theoretical frameworks from Legitimation Code Theory and Systemic Functional Linguistics to explore their implications for teacher training. Specifically, it links one Year 11 Biology teacher's experience of new metalanguage and explicit pedagogy, in teacher training, to first attempts at classroom Joint Construction, a form of collaborative text creation. This paper then raises important issues regarding collaborations concerned with classroom interaction and knowledge-building practices. (Contains 4 tables and 8 figures.)