I am wondering if there is any scientific evidence showing that forgiveness education might increase academic achievement.
Yes, there is scientific evidence specifically concerning adolescents who are at-risk for academic failure. In the first study below, the students went from a D+ average to a C+ average. The second study was done in South Korea. Some of the participants were in a correctional institution.
Gambaro, M.E., Enright, R.D., Baskin, T.A., & Klatt, J. (2008). Can school-based forgiveness counseling improve conduct and academic achievement in academically at-risk adolescents? Journal of Research in Education, 18, 16-27.
Park, J.H., Enright, R.D., Essex, M.J., Zahn-Waxler, C., & Klatt, J.S. (2013). Forgiveness intervention for female South Korean adolescent aggressive victims. Journal of Applied Developmental Psychology, 20, 393-402.