High quality afterschool programs foster academic and socio-emotional development in middle childhood and adolescence. The success of these programs is dependent on the skills and competencies of program staff. High quality programs require staff who are able to sustain supportive relationships with young people, foster positive relationships among students, and provide engaging, challenging activities that build on student interests. This paper outlines the core competences and mindsets of staff as the cornerstone of high quality programs and proposes strategies to develop these staff proficiencies more broadly. Testing these strategies can provide rich opportunities for researchers to collaborate with practitioners to design and implement effective approaches to professional development in extended education settings.