There is a long tradition of teaching science through inquiry, with broad agreement about the form it should take. Students should investigate researchable questions; gather and analyse data; and develop and represent evidence-based claims. Authoritative teacher or textbook representations are generally used to guide this learning (Buckley & Boulter, 2000; Bybee, 1997; Furtak et al., 2012; Sell et al., 2006). Parallel to this approach, teachers have also guided students to construct, review and refine their own representations, leading to learning gains. However, this student representation construction approach poses new challenges for teachers. The teacher is expected to elicit and guide students' reasoning about their own represented claims as an orientation to understanding and learning scientific forms of reasoning and their representation. In this paper, drawing on our initial account of this pedagogy, we aim to clarify further this approach's rationale and teacher strategies and underlying purposes in key early stages of exploration in the topics of chemistry and mathematics with a Grade 5 class. An interdisciplinary focus was used to guide students' learning about the science concepts of states of matter, evaporation and the mathematical concepts of formal and informal measurement and data representation. Analysed data included video capture of the teacher's guidance of tasks and classroom discussion, student artefacts and teacher and student interviews. We identify how the teacher framed the task, oriented student inquiry and guided evaluation of students' representations through implicit and explicit instruction.