This article focuses on a neglected topic in the historical sociology of childhood, namely health education, and explores a neglected theme, namely the gendered character of (re)constructions of childhood. Drawing on primary sources, the article argues that while health education for children played an important role in a broader set of British national, political strategies to ensure the health and fitness of "the Nation" during the 20th century, it was girls who were the primary targets and recipients. Gender was thus central to the "body work" in childhood that the official publications on health education sought to promote.