Light is a topic that is often taught in year 3 (ages 7-8) in English schools, where children learn that light is needed for us to see, that it can be reflected from shiny surfaces and that shadows form when light is blocked by an object. They may also have some experience of how the size of shadows changes when the distance between a light source and object is changed. Helpful resources to support teaching children about light have been developed by PLAN and STEM learning. This short article reports on a year 6 (ages 10-11) lesson that focused on investigating shadows. Children enhanced their 'working scientifically' skills by applying mathematical knowledge. A quantitative approach was used so that children could generate, record and plot data and develop an understanding of variable correlation and causation.