There is growing evidence that participating in extracurricular and out-of-school activities during adolescence is associated with both short- and long-term indicators of positive development (e.g., Eccles & Barber, 1999; Eccles & Templeton, 2002; Mahoney, 2000). Yet, few researchers have questioned whether these relations are solely the result of activity participation during adolescence or if they are the culmination of a process that began in middle childhood. Middle childhood is marked by many physical, cognitive, social, and contextual changes. It is during this time that children develop multiple cognitive skills, such as reasoning and the ability to reflect on one's accomplishments, experiences, and aspirations. Children's social worlds broaden as they begin to participate in organized out-of-school activities. The changes in children's abilities and skills coupled with the new contexts in which children develop suggest that middle childhood is an important period for the development of skills and beliefs through participation in out-of-school activities. Although entry into adolescence and adulthood brings new abilities and interests, some of the benefits of adolescent participation may not be realized unless the groundwork is laid in middle childhood.

There is little evidence available concerning developmental hypotheses about the reasons or mechanisms for these associations. Longitudinal studies over extended periods of time afford an opportunity to examine positive and negative consequences of participation based on activity characteristics as well as other potential influences such as parental encouragement or child talent.