The paper deepens the role of the external evaluation of schools as a lever for the improvement of the education system. A qualitative systematic review of literature based on the PRISMA method selected 20 contributions related to the impacts of external evaluation on school processes. The study explores external evaluation practices carried out in different European countries, highlighting a marked heterogeneity in the impact of these processes and showing how external evaluation may be able to generate long-term positive effects on organizational change and decision-making processes. The analysis found that the perception of quality by recipients, fairness and transparency in the feedback from external evaluation and inspection visits, stakeholder involvement and change-oriented leadership of the school leader can be key elements in implementing improvement actions.