Background: Children with poor social-emotional health are at risk of failing to reach their potential. Method: The impact of the Pyramid Club year 3 preventive intervention on children’s social-emotional health was investigated. Children were allocated to an intervention or non-problem comparison group. Results: Post-intervention both groups had improved Total Difficulty scores (Strengths and Difficulties Questionnaire) with the Pyramid group showing a significantly stronger effect size (r = .71) than the non-problem comparison group (r = .44). Conclusions: The Pyramid Club intervention improves the social-emotional health of vulnerable children. The need to evaluate such interventions and to extend research are discussed.