Developing argumentation-based inquiry practices requires teachers and students to be explicit about classroom norms that support these practices. In this study, we asked: "How can a teacher scaffold the development of argumentation-based inquiry norms and practices in a mathematics classroom?" A primary classroom (aged 9-10) was videotaped during the school year to address this question. Using key features of scaffolding (diagnosis, responsiveness, handover to independence) we analysed strategies the teacher used to establish the required norms and practices. Interviewed reflections from the teacher provided further insights into her intentions and adaptive responses to students' emerging practices. The analysis showed how the teacher constantly diagnosed the classroom norms and responsively used strategies that changed as norms emerged, developed and stabilised. After nine months, there was evidence of argumentation-based inquiry norms practiced by students, independent of the teacher's presence.