Using an exercise book annotated by teenagers in the 4th form, this article shows how the latter enter into a problematic of sexual investment of an objectal nature, through various types of relations – narcissistic, homosexual and heterosexual – by using play and humour. Keeping a certain continuity with the obscene folklore of elementary school children, teenagers use school as a place for learning about adult sexuality away from the family, which has become unfit for sexual objectal investment, and from peer groups too much centred on homophilia.