Conceptual challenge is often considered a necessary ingredient for promoting deep learning in an inquiry-based environment. However, challenge alone does not support conceptual development. In this paper, we draw on complexity theory as a theoretical lens to explore how a primary teacher facilitated students' conceptual change through repeated cycles of challenge and support to develop increasingly robust concepts. Data are drawn from a primary class as they were developing initial understandings of distribution, informal statistical inference and sampling variability in the process of solving an extended mathematical inquiry problem. Data included classroom video, researcher journal and student work samples. The findings suggest two benefits to guiding students through multiple iterations of challenge and guidance: the opportunity to provoke and guide richer mathematical concepts; and the opportunity to provide earlier exposure to advanced mathematical concepts. Building on this research, we argue for the value of multiple iterations of challenge-support phases to develop increasingly robust understanding over time.