The amount and nature of sex education provided varies from school to school. Teachers regard it as fraught with difficulties. It is a sensitive subject, there is no statutory training, no set curriculum or examinations to work towards, and it is one of many areas to be dealt with in an increasingly crowded Personal and Social Education programme by teachers who often also have a guidance role and a subject commitment. Drawing on data from 25 schools in Scotland, this paper considers how teachers talk about sex education, and looks at the factors that shape provision, at the school and teacher levels. The broad priorities of the senior management team, and the views and experience of key individuals, shape programme design. Within schools, the values, experiences and characteristics of individual classroom teachers are important in understanding what sex education is actually delivered, particularly where the Guidance Team lacks cohesion.