Previous research suggests that elementary teachers vary in their enactment of science curriculum materials and may not always engage students in substantive sense making. This mixed-methods study investigates elementary teachers' use of science curriculum materials to engage students in the scientific practice of comparing and evaluating evidence-based explanations. We asked (1) How do in-service elementary teachers use existing science curriculum materials to engage students in comparing and evaluating evidence-based explanations? and (2) What do their instructional design practices reveal about their pedagogical reasoning for engaging students in comparing and evaluating evidence-based explanations? Our results suggest that comparing and evaluating explanations was the least-emphasized feature of inquiry in these teachers' planned and enacted science instruction. Though the teachers made small adjustments that better engaged students in the practice, their curriculum materials and ideas about comparing and evaluating evidence-based explanations limited the impact of their curriculum design decisions on students' sense-making opportunities. (Contains 3 notes, 3 figures, and 4 tables.)