This paper presents data on the need for sexual health information and advice of 4353 students aged 13/14 years in 13 English secondary schools. Data were collected by peer educators as part of a sex education programme, and through a questionnaire survey administered by researchers. Data illustrate young people's need for concrete information and advice on issues related to physical development and puberty; transmission of sexually transmitted diseases; accessing and using condoms and other contraception; using sexual health services; managing relationships and dealing with jealousy, love and sexual attraction; how people have sex; sexual pleasure; masturbation; and homosexuality. Differences between the concerns and interests raised by young people and current UK guidance on sex and relationships education are examined, and the implications of these findings for designing future policy and effective school based sex education programmes are discussed. The paper highlights some of the wider social norms around sex and sexuality that influence young people's understanding and sexual behaviour, and the importance of addressing these within sex education is noted. Factors influencing the processes of expressing and assessing needs are explored.