Purpose: Adopting an ecological perspective, the study explored the context-strengths of three successful school-based TDEs in rugby league. Method: Utilizing a mixed methods approach, incorporating validated psychometric questionnaires (N = 118) and semi-structured interviews, various stakeholder perspectives (N = 30; i.e., current/past students and coaches) were triangulated and corroborated to identify TDE ecological strengths. Results: Compared to benchmark TDE data, and supplemented by descriptions of TDE features and processes, results confirmed strong coherence to "effective" factors in TDE literature. Collective "ecological strengths" included quantitative findings of a highly supportive culture, shared "person" and "athlete" desired outcomes, and a long-term focus; and qualitative features of high behavioral expectations, strong values of hard work, and the promotion of personal ownership in athlete development. Opportunities to enhance TDE effectiveness were also identified, with psychological skill development (e.g., self-reflection, coping) and balancing intra-rugby league pathway demands (i.e., competition/training loads) highlighted. Conclusion: Findings identify characteristics, components, and processes of school-TDE environments associated with successful athlete development in schools and beyond (i.e., transition into an athlete development pathway).