Student-centered activity in education has the potential to promote constructivist learning. However, how students engage in the activities and respond to classroom cues can mediate the degree to which constructivist thinking and learning occur. Research on constructivist-oriented instruction and learning tends to focus on activity itself and student responses to the activity as a bound unit of analysis. While much has come out of this research, there still exists the need to understand how students engage in student-centered, constructivist activity in the classroom. The present study assessed the influence of key teaching-learning resources on student engagement during student-centered activity. Model-based instruction provides the framework for student-centered, constructivist activity in a sixth grade class at a public school. On four separate occasions students generated visual models as artifacts to demonstrate their understanding during a unit on microorganisms. The models were analyzed for common class-wide patterns as well as differences in specific student responses. Teacher behavior and prompts were compared with that analysis to interpret differences between enactments. Students did not fully demonstrate constructivist thinking as anticipated, but constructivist elements and other emergent behaviors were identified. Key areas that influenced modeling behavior included framing a problem, receiving feedback, and receiving scaffolded support. Students elaborated their models through scaffolded conversations with the teacher. Student-teacher interactions to elicit constructivist modeling indicated a cognitive apprenticeship for helping students reason via model construction. Findings suggest a need for research that examines how students grow in modeling skills and in reasoning skills during model construction.