Has forgiveness education in schools been studied scientifically and found to be useful?
Yes, there is evidence. I actually answered this in another question posed to me here on October 29, 2022. Here is that answer:
Yes, there now are scientifically-based forgiveness programs, many of which focus on stories and story characters who experience conflict and learn to resolve those conflicts. The research shows that children and adolescents, when given a sufficient amount of time (12 or more weeks) to think about forgiveness, actually forgive to a deeper level than before they had these programs. Here is a reference to a journal article showing this to be the case: Rapp, H., Wang Xu, J., & Enright, R.D. (2022). A meta-analysis of forgiveness education interventions’ effects on forgiveness and anger in children and adolescents. Child Development.