The development of students' reasoning and argumentation skills in school science is currently attracting strong research interest. In this paper we report on a study where we aimed to investigate student learning on the topic of motion when students, guided by their teacher, responded to a sequence of representational challenges in which their representational claims functioned as both process and product for reasoning about this topic. This qualitative case study entailed collection of data through classroom observation, transcripts of student/teacher interactions, and interviews with teacher and students. We found that students participated in various reasoning processes in generating and critiquing their own and other students' representations on the topic of motion, contributing to positive engagement with the topic and conceptual understanding. We identified several pedagogical principles that support this learning.