In Sweden, as in the other Nordic countries, a great many children and young people are members of a sports association (77% in the age group 6–12 years and 41% in the age group 13–25 years). Physical activity levels are high compared to other European countries (CIF, 2018a; European Commission, 2010; 2014). However, participation in sports associations has decreased in recent years, and the decline is more prominent among older youth and girls (CIF, 2018b). Furthermore, there is a strong polarization between groups who are very active and others who are inactive. How can this development be understood? Sports associations are not alone in losing members. Over 20 years ago, in 1995, Robert D. Putnam described a reduction in all forms of in-person social interaction in the US, and an analogous development can be seen in Sweden (Putnam, 1995; Trägårdh, 2007). Yet while participation in sports associations decreases, an increasing number of young people claim to be interested in physical exercise, stating that they exercise several times a week. Clearly, association sports activities are challenged by commercial enterprises (CIF, 2014a; 2014b). It has been argued that the activities offered by the sports associations are the reason for this development. A narrow focus on results and performance may alienate some children and young people, who become uninterested in sport and physical activity (Redelius, 2011; 2013; Norberg and Redelius, 2012; Thedin Jakobsson, 2013). In addition, sports activities may be socially, psychologically, and physiologically harmful for children and young people (Fasting, Brackenridge, and Kjølberg, 2013). Here I want to challenge this understanding of why children leave organized sport using insights from the sociology of childhood. Instead of focusing on polarized expectations – democratic fostering and sport for all in contrast to the fostering of elite athletes – this study will propose an alternate explanation focusing on the changing understanding of childhood in the Nordic, and more specifically Swedish context.