This paper concerns the response to the sex education film "Growing Up", made in 1971 by Dr Martin Cole, which used a combination of animation and live action to offer a frank and uncompromising account of sexual reproduction. As part of this, both male and female masturbation and an unsimulated act of male-female coitus featured in the film. Cole was widely denounced both by religious conservatives including the members of the Nationwide Festival of Light and by others involved in sex education. The former objected to what they took to be his promotion of precocious and promiscuous sex, and the latter charged him with setting back the cause of "responsible" sex education by years or decades. However, evidence from various schools in which "Growing Up" was seen suggests that it was apparently well received by pupils. But an "ad hoc" alliance of religious conservatives and "responsible" sex educators ensured that "Growing Up" was not widely distributed, and a tactic agreement of sorts has arisen that such explicit sexual imagery will not be featured in school sex education materials in the United Kingdom. Sources include selected media reports/discussions, parliamentary debates, letters sent to Cole, teachers' comments and an interview conducted in 2007. (Contains 12 notes.)