Children with externalized behavioral problems (BP) are at increased risk of being affected by a lack of social skills and academic engagement, and reading difficulties can frequently occur. Peer-tutoring (PT) interventions demonstrably promote both positive behavior and academic outcomes. To foster these effects, using interdependent group-reward contingencies appears to be a promising approach -- especially for children with BP. In the current single-case study, a paired and repeated reading strategy was supplemented with the German version of the Good Behavior Game (GBG). A multiple-baseline design was used for evaluation. The study examined how the academic engagement, respectful behavior, disruptive behavior and reading fluency of four tutors and four tutees with BP (second and third grades) developed when the GBG was played in addition to PT. The results reveal that the tutors and tutees showed more academic engagement and less disruptive behavior. With regard to the tutees' reading fluency, significant small to medium effects can be attributed to the GBG.