This study evaluated a life skill training program on school violence given to elementary school children. A quasi-experimental study was conducted, and a 12-week intervention was implemented targeting 70 students aged between 10 and 11 years. The instruments included peer competency, attitudes toward school violence, experience of school violence, and the Self-Control Rating Scale. The data were analyzed using repeated measure analysis of variance. A significant difference was observed between the groups over time on peer competency (F = 4.17, p = 0.020), attitudes toward school violence (F = 6.02, p = 0.004), and violence experience as a victim (F = 3.49, p = 0.036) and as a perpetrator (F = 3.87, p = 0.026). In the experimental group, the mean scores for peer competency increased compared to the control group, whereas school violence experience decreased at the posttests. A 12-week program of life skill training offered to children was effective in promoting peer competency and attitudes toward school violence, while decreasing the experience of school violence.