A tension in designing classroom learning involves balancing the questions and interests of students with the goals of teachers and standards. One approach to navigating this tension in science classrooms is to simultaneously support and constrain students' questions about an observable natural phenomenon in the classroom and then take up those questions throughout a unit of instruction. Analyses of students' questions at the start of a middle school science unit and their responses to surveys throughout the unit suggest that students perceive that their questions are indeed driving learning, suggesting the promise of supporting students' epistemic agency through co-construction of questions, ideas, and investigations in storylines. [This paper was published in: "13th International Conference of the Learning Sciences (ICLS), Vol. 1," edited by J. Kay & R. Lukin, International Society of the Learning Sciences, 2018, pp. 25-32.]