This study investigated the effects of bullying victimization on cognitive, school engagement, and friendship outcomes using panel data collected from elementary school students in a Japanese city. Employing a value-added model that controls for prior outcomes, our findings revealed that bullying victimization significantly impairs both cognitive and school engagement and weakens friendship formation. Furthermore, a high prevalence of bullying victimization within the classroom was found to negatively impact cognitive outcomes in subsequent years. These findings underscore the importance of effective school bullying prevention in fostering human and social capital among school-aged children.