This paper reports on a teacher professional development (PD) programme addressing dialogic argumentation in mathematics and

Whereas science is fundamentally a result of a dialogic debate, the authoritative approach has been conceived of as a fundamental part of school science. Dialogic interactions encompass the mutual appreciation of different ideas manifested in teacher supportiveness toward students and, in authoritative interactions, the focus is more on the science's or teacher's point of view.Whereas dialogic and authoritative interactions have been viewed as oppositional in recent educational research, authoritative interactions could well be the seed for and give strength and meaning to dialogic interactions, and thus, to the overall dialogue. The focus in this study is on the interplay between authoritative and dialogic interactions rather than on the rivalry between them. In other words, we present how both dialogic and authoritative interactions can be essential for teacher orchestration of whole-class discussions. This is achieved through a temporal consideration of the interactions and an in-depth analysis of selected episodes of a case science teacher. Interpretations are complemented with teacher reflections to shed light on the on-the-fly decisions made by the teacher when orchestrating dialogue. Implications for educational research and teacher education are discussed.

Three dimensions of dialogicity are emphasised in the literature: dialogic teacher talk, students' dialogic moves and organising for dialogic teaching. In this article, we examine these dimensions and the interplay between them in supporting dialogic argumentation in the context of whole-class discussions in mathematics and physics. Three seemingly different seventh-grade lessons were selected for further analysis from the database of a research project on dialogic argumentation. In this paper, we focus on whole-class discussions after a group assignment. The lessons were video recorded with multiple cameras and transcribed. We characterised dialogic features of teacher talk, more general teacher decisions and organising for dialogic teaching, as well as students' dialogic and justifying moves. In addition, we examined how these were connected. According to the results, the three dimensions of dialogicity played out differently in the lessons. Furthermore, the results give insights into the interplay of the three dialogicity dimensions and students' justifying moves in dialogic argumentation.

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