Based on three cross-sectional field studies conducted in the German state of Thuringia, this dissertation thesis followed two primary research aims. First, it aimed at exploring the importance of group-related justice perceptions for students’ adjustment to a school merger. Second, it was intended to examine the cognitive-motivational antecedents of these group-related justice perceptions. Taken together, this line of research extends previous literature twofold. From an applied perspective, this thesis provides an insight into relevant social psychological processes affecting the success of a merger in an educational setting. From a theoretical perspective, it contributes to examine the validity of social psychological approaches to justice and identity in the specific educational field of a school merger.