This paper offers a synthesis of research evidence around teaching light to primary and secondary school pupils as part of the Institute of Physics Promoting and Interpreting Physics Education Research (PIPER) project. Conceptual change literature describes many of the difficulties young people can have understanding the phenomenon of light, and this knowledge can be useful in the classroom. Pupil-teacher dialogue is used to illustrate some of the pedagogical challenges teachers face in this topic. This paper also highlights the range of influences on pupils from everyday life and from the classroom, with a view to promoting teacher awareness of conceptual change research evidence.