This report characterizes forms of dialogic support that a sixth-grade teacher generated during whole-class and small-group conversations to help students develop a practice of statistical modeling. During four weeks of instruction, students constructed and revised models to account for variability and uncertainty across a variety of random processes, many of which they experienced first-hand. Data sources for the research included field notes and video recordings of classroom conversations involving the teacher. Analyses identified and characterized teacher assistance during classroom episodes in which the teacher fostered the emergence and development of fundamental aspects of statistical modeling practice. These aspects included a) establishing mappings between models of chance and the situations or processes being modeled, b) imagining outcomes as constituents of a long-run random process, c) evaluating model fit, and d) making model-based inferences. Throughout instruction, the teacher systematically helped students coordinate these distinctive aspects of modeling practice. The findings suggest how teacher practices can promote the sustained development of statistical reasoning as a dialogue between data and model, and more generally, how teacher assistance attuned to student thinking about aspects of a disciplinary practice can foster a student-centered phenomenology of that practice.