Despite its recommended use, physical activity promotion in the academic classroom (PAPAC) has received little attention in terms of the factors that help to facilitate it. In this study, a social learning perspective was adopted to examine the role of physical activity biographies in generalist classroom teachers' (CTs) PAPAC. CTs (N = 213) were assessed on their satisfaction with personal K-12 physical education (PE) experiences, perceived physical activity competence, self-reported physical activity, perceived PAPAC competence, and self-reported PAPAC. Structural equation modeling supported the hypothesized relationships between variables. Specifically, PE satisfaction predicted physical activity competence, which in turn predicted physical activity. Subsequently, physical activity predicted PAPAC competence, which predicted PAPAC. The specified model explained 41% of the variance in PAPAC, with PAPAC competence being the largest contributor. This study provides useful information for designing interventions to increase PAPAC, as it stresses the need to identify strategies that improve CTs' physical activity-related, and PAPAC-related self-perceptions.