Research in the field of technology-enhanced learning has argued for a broader scope of technology-supported learning environments to include the design of activity systems which position students as active thinkers by reorganizing learning with technology around the practices of scholarly communities. In the context of elementary ecosystems science, this entails structuring classroom activity around the construction and evaluation of epistemic artifacts, such as scientific models and representations, that profitably direct learners' conceptual efforts toward productive forms of inquiry and the construction of new scientific knowledge. In this demonstration-of-concept paper, we present EcoMOD, an elementary ecosystems science curriculum that blends an immersive virtual environment with an agent-based computational modeling tool to support growth in ecological knowledge and scientific practice in learners aged 8 to 11 years old. Specifically, we explore how the design of the EcoMOD activity system supported students' active thinking in scientific inquiry through transformative modeling practices. Analysis of student activity and discourse indicates that engagement in transformative activities supported students in developing more nuanced causal explanations of the ecosystem by the end of the curriculum.