This CPD unit explores argument as a teaching and learning strategy for primary science. The unit is supported by classroom materials, designed to introduce children to using argument. It explains how these materials can be used to improve transition from Year 6 to Year 7. While the supporting materials have been created to promote positive transition, they work equally well as stand alone teaching resources. Where they are to be used for transition, it is recommended that this unit is viewed by primary and secondary colleagues together.