School mediation is a peacekeeping, conflict-resolution procedure. Evaluating mediation processes allows us to assess their effects through their participants. This systematic review of studies of school mediation aims to study what evidence exist on its educational benefits for teacher mediators, student mediators, and mediated students. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) method was followed to ensure the transparency and reproducibility of the results. In total, 524 were initially identified, of which 141 were retained after screening. Of these, 32 studies were published from 2000 to 2020. The studies were analyzed according to their statistical design. In addition, their results were summarized along the following dimensions: interpersonal emotional, personal emotional, cognitive-moral, and social impact. School mediation has a personal impact that increases the likelihood of acting constructively and positively when facing conflicts.