The reluctance of parents to provide sex education has been a problem for educators since the first attempts at the modernisation of sex education in the early twentieth century, yet the sexual needs, desires and fears of parents are rarely even mentioned in pedagogical debates. This article examines the intense anxiety and embarrassment felt by both parents and teachers when they tried to provide sex education in mid-twentieth-century England. The gendered sexual cultures of women and men and the way in which these shaped responses to the pubertal experience of girls and boys are described. Sex education was a rational progressive discourse; the response of sex educators to resistance and rejection of what they offered was to present "rational" arguments explaining that these anxieties are unnecessary and can thus be abandoned. Waves of popular emotion concerning child sexual abuse since the 1980s demonstrate the continuing relevance of this fear and anxiety, emotions that shaped the course of sex education over the past century.