Moderation is put forward as they key strategy for improving the reliability of teacher assessment. However, for many teachers the word "moderation" conjures up ideas of uncomfortable situations in which marking is being checked by others and there are prolonged arguments about tiny features of individual work. In this article, the author argues that moderation can be viewed differently: as an opportunity for professional learning that will build confidence, and the reliability of teacher assessment in the longer term, rather than a stand-alone checking exercise. She shares three examples of moderation activities the she has used to support discussions about assessment in primary science. [This article was written with Kendra McMahon.]