The Talking Science project initially involved three secondary schools and eight of their feeder primary schools in the London Borough of Richmond Upon Thames. The project created, trialled and evaluated a set of key stage 2/3 transition materials for children moving from primary to secondary school, using argument as a teaching and learning strategy. Last year all schools in the Borough of Richmond used the materials as part of their provision for key stage 2/3 transition. Although the materials have been designed to be used to improve school transition, they are also a valuable stand-alone teaching resource for using argument. Argument involves the children engaging with the language of science, including generating and justifying their claims to knowledge. Children's experiences are often counterintuitive to accepted scientific ideas and "argument" offers opportunities for them to explain, giving evidence for their ideas. Following the project funded by the AstraZeneca Science Teaching Trust, the author discusses improving primary to secondary school transition through an argument-based approach to teaching science. (Contains 3 figures.)