'Centre' is a key conceptual understanding that students require to think and reason statistically. In this study, a class of young students (aged 9-10) who had predominantly procedural experience with statistics, was posed a complex problem regarding the best design for a catapult aeroplane. The context established an opportunity for students to engage authentically with data modelling. Analysis of lesson videotape and work samples provided insight into students' developing understandings as they worked with dot plots and hat plots to focus on the notion of 'middle'. Insights into students' thinking and reasoning are discussed as the students engage in constructing, interpreting and predicting from statistical models. This research has implications for statistics curriculum in the early formal years.