Although the law requires the employer to assess the risks, the person who knows the circumstances of the lesson well enough to do this is the science teacher. Only the teacher knows what s/he plans to do and can make a judgement about her/his own skills and the experiences, skills and potential behaviour of the classes taught. Although the department may have come to some collective decisions when producing a scheme of work, the individual teacher still needs to think about the particular circumstances of her/his own lesson. In this article, the author describes a system for assessing risk in science lessons, enumerates three elements involved in assessing risk, and discusses how teachers can reduce the risk. The author also shares how to customise a model risk assessment and where to find model risk assessments.