The study examines the perspective of cultural history, representations of childhood, set out in discursive movement between the late nineteenth century and early decades of the twentieth century. It takes as its object of analysis the book entitled What a boy should know, of Sylvanus Stall, published in 1897 and part of the collection Sex and Self Series. The book circulated in Brazil in its first edition in 1919. Was aimed at children, announced its commitment to help them have a childhood, pure and holy. Through reading books offered in this period were produced and circulated varied contents, especially those related to religion, morals, health, hygiene, sexuality, among others. The book is a manual for life preparation and defense of the importance of chastity of boys, a guide to good living. Dedicated to the production of different extracts a child walking toward a youth and adulthood, strengthened by readings decent and pious, medical scientific explanations and moral lessons.