Assessing children's learning is a key part of teaching. In all curriculum areas it is used for informing planning of future learning experiences and assessing pupil progress. Specifically in science, it identifies knowledge and understanding of scientific concepts, reasoning, and practical skill development. There are various ways to assess, including formative ongoing teacher assessment using evidence from verbal responses to questioning and observations of practical tasks. The use of an activity circus, with its visual stimuli and related questions, is a very child-friendly and informative means of gathering assessment information. It also allows opportunity to differentiate assessment across the spectrum of ability, from gifted and talented to special educational needs. (Contains 4 figures, 2 boxes, and 6 online resources.)