Writing in 1927, five leading scholars and administrators of the Australian schooling systems published a book entitled "Education in Australia: a comparative study of the educational systems of the six Australian states". These authors wrote of Australian education in a time of great optimism, and one of the key areas of reform they addressed was the introduction of forms of post-primary schooling for a "problem" population of 12-15-year-olds who were not attracted to, or staying with, the high school curriculum which led towards university study. Through the lens of "Education in Australia", this paper undertakes a genealogical exploration of the way the adolescent emerged as an object of school reforms in the early twentieth century and shows that these reforms were articulated with discourses of race, social efficiency, science and culture. (Contains 3 notes, 1 figure and 1 table.)