Clinical scientists are calling for strong partnerships in the provision of evidence-based treatments for child mental health problems in real-world contexts. In the present study, we describe the implementation of a cognitive-behavioral intervention (CBI) to address grade 5 children’s anxiety symptoms. The CBI arose from a long-standing partnership between University and Education Department stakeholders. The partnership integrates school-based, evidence-informed treatment delivery with clinical education, and also supports a school-based psychology clinic to provide assessment and treatment services to children attending schools within the catchment area and clinical training for university graduate students. Children in the active condition (N = 74) completed the CBI during regular class time, while children in the control condition (N = 77) received the standard classroom curriculum. Children’s anxiety and depressive symptoms, threat interpretation biases (perceived danger and coping ability), and perceptions of their social skills were assessed before and after condition. Children in the active condition reported significant improvements in self-reported anxiety symptoms, and perceptions of their social skills and coping ability, whereas no significant differences were observed for children in the control condition from pre- to post-assessment. For a subset of children assessed 12 months after the CBI (n = 76), symptom improvement remained stable over time and estimates of danger and coping ability showed even greater improvement. Results demonstrate the value of strong stakeholder partnerships in innovative youth mental health services, positive child outcomes, and clinical education.