Bullying in schools is a major health concern throughout the world, contributing to poor educational and mental health outcomes. School nurses are well placed to facilitate the implementation and evaluation of bullying prevention strategies. To evaluate the effect of such strategies, it is necessary to measure children’s behavior over time. This scoping review of instruments that measure the self-report of aggressive behavior and bullying by children will inform the evaluation of bullying interventions. This review aimed to identify validated instruments that measure aggression and bullying among preadolescent children (age 8–12). The review was part of a larger study that sought to differentiate bullying from aggressive behavior by measuring the self-report of power imbalance between the aggressor and the child being bullied. The measurement of power imbalance was therefore a key aspect of the scoping review.