Research into students' conception often presents those conceptions as problematic for the teacher, something to be exposed and then overcome through instruction. This article argues for a different approach to conceptual change instruction-one that places students' science conceptions and their ability to reflect on their conceptions at the center of science instruction. In the elementary school classroom selected for this study, students learned to speak about their conceptions in powerful ways (i.e., to be metacognitive) when studying the physical science concepts of force and motion. Students in this classroom defined the status constructs of intelligibility and plausibility in response to their teacher's instruction and then applied both constructs when speaking about ideas related to force and motion. When using the status constructs, these students provided deep insights into their developing conceptions of force and motion and how they were learning these concepts. Comments from the students helped the teacher evaluate their progress and allowed her to plan instruction based on the students' progress. Learning outcomes for students in this classroom included changes in their abilities to apply status constructs to their developing notions of force and motion. The instructional approach selected by this teacher also supported change in students from passively receiving information to actively examining their own conceptions. The role of the teacher in facilitating this approach to conceptual change instruction shifted from the more traditional one of organizing and sequencing science content knowledge to a more dynamic role, one that was capable of responding to the ideas expressed by students. These new roles required that the teacher provide metacognitive tools such as intelligibility and plausibility as part of her instruction and that students learn to apply these tools when discussing science concepts.