A first step in analyzing educational growth is identifying the desired ends of growth. We have argued that the goal of epistemic education should be to promote apt epistemic performance, defined as performance that successfully achieves epistemic aims through competence (Authors, 2018), and have identified five aspects of epistemic competence that can jointly enable successful epistemic performance. We expect that dialogic instruction that addresses all five aspects will promote students’ epistemic competence. Hence, the objectives of our study are: 1. To identify indicators of growth in apt epistemic performance in student discourse during model-based inquiry in science, and 2. to identify teacher moves that promote or hinder the development of students’ apt epistemic performance. Based on classroom discussions of seventh graders in a model-based inquiry curriculum, we identified two teachers, one of whom appeared to be effective at engendering epistemic discourse among students, and one of whom appeared to be ineffective. We assessed student discourse and teacher discourse and moves along the five aspects of apt epistemic performance to identify the differences in the teachers’ methods of promoting epistemic growth, and the differences in the engagement of students in the two classrooms with epistemic discourse. Our data demonstrate students’ epistemic progress and how teacher comments elicit student discourse within the five aspects of apt epistemic performance. For example, the more effective teacher often guided students to autonomously arbitrate knowledge quality and discussed good epistemic practices with students, while the less effective teacher often arbitrated knowledge himself and missed opportunities to help students understand epistemic practices. Our results will establish an empirically grounded approach for evaluating dialogic instruction based on assessing the aptness of students’ epistemic performance and the extent to which instruction promotes such apt performance.
