The environmental education (EE) field has encountered persistent challenges in fostering the integration of EE practices in public schools, a challenge that may be addressed through integration of EE with the Next Generation Science Standards (NGSS) in the United States. In addition to the potential for fostering EE, the integration of EE and NGSS may provide a unique set of conditions for understanding how and why teachers shift their practice to incorporate more EE in their classrooms. Using a mixed methodology research design, this study examines the outcomes and processes of a professional development institute that integrated NGSS and student-driven environmental stewardship. This study provides evidence that integrating NGSS Science and Engineering Practices with stewardship may help infuse EE into classrooms. The research also contributes to theoretical understanding of the processes by which professional development shapes teacher change within an organizational context. Specifically, teacher instructional change was predicated on a shift in their beliefs that stewardship was possible in a standards and accountability-based educational context. The requisite shift in beliefs came about through the expectations and supportive resources provided by the professional development, teacher observation of student engagement, and the justification NGSS integration provided for stewardship activities.