The effectiveness of universal social emotional learning (SEL) programs are dependent on the incorporation of best practice principles, including an evaluative component. In the present study, the effects of a best practice, teacher-led SEL program was examined with 854 children aged 8–12 years. KooLKIDS uses an interactive multimedia format and animated character to help children develop their emotion regulation capacities, social and friendship skills, empathy and compassion for others, and self-esteem. A quasi-experimental waitlist-control design was used to examine the impact of KooLKIDS on social and emotional competence, behavioral and emotional problems, academic achievement and effort. Hierarchical linear modeling demonstrated significant increases in social and emotional competence, and reductions in internalizing and externalizing problems in children post KooLKIDS program in the intervention group. The findings suggest that KooLKIDS has strong potential as a teacher-led, classroom-based, structured program for enhancing children's social and emotional learning.