While astronomy has recently re-emerged in many science curricula, there remain unresolved teaching and learning difficulties peculiar to astronomy education. This paper argues that mental model building, the core process in astronomy itself, should be reflected in astronomy education. Also, this crucial skill may promote a better understanding of the nature of science by pupils and it resonates with current understandings about pupils' learning in science. However, three practical questions to be considered are: the expressed reservations about the connection between mental model building and meaningful learning; the earliest age of pupils for whom mental model building is appropriate; and the lack of research into pupils' prior ideas about the role of models in science. The paper describes how a four-phase general pedagogical strategy was adopted to create an astronomy teaching and learning package to promote mental model building. The package consists of notes explaining the mental model building followed by an overview of the teaching-learning approach and suggested outlines of the 12 lessons. Research investigated whether that package can help Year 7-8 pupils interrogate and refine their mental models of the Sun-Earth-Moon system within the constraints of an ordinary class of 33 pupils. The results showed that all four phases of the general strategy were necessary and effective in that most pupils were able successively and successfully to critique their mental models of the Sun-Earth-Moon system while also achieving traditional astronomy knowledge goals. Implications are that pupils as young as Year 7-8 may be able to construct other appropriate mental models, such as those for biological populations, atomic structure and plate tectonics.