It is the view of these authors that children learn to be peacebuilders in the context of relationships where, if fortunate, they experience guided practice in interpersonal skill development around conflict. "Mediator Mentors", the program described in this article, is a school-university partnership in which Teacher-Education Candidates, Peace and Conflict Studies interns and classroom teachers had as their overall objective improvement of the learning climate through peer mediation program implementation. Social-emotional variables like empathy and perspective-taking were considered measurable outcomes, Analysis of pre-to-post change scores revealed that mediators demonstrated significantly higher gains on measures of social-cognitive development F (3,67) = 19.26, p. less than 0.000 when compared to non-mediators. Although mediators and non-mediators (N = 70) scored no differently at pretest, the difference was highly significant at posttest. Students serving their school in the mediator role also reported more positive perceptions of school safety than did non mediators. Being a mediator was also significantly associated with higher language arts scores as measured by standardized testing (r = 0.60, p less than 0.000). And finally, mediators described their home-lives as more peaceful (at posttest, though not at pretest), than did non mediators. (Contains 2 figures and 1 table.)