In 2012, the authors took responsibility for a CS1 course with 45 students. This experience report reviews the subsequent 10-year learning process of engaging undergraduate students to facilitate small-group teaching and to design and develop an online learning environment to conduct what became our university’s flagship CS1 course, currently enrolling 749 students. The course inherited an emphasis on experiential learning from its role model, MIT’s 6.001. The size of the learning groups is limited to eight students per group, which currently requires a team of 105 student facilitators. The resulting need for student engagement and scaling motivated the development of a new web-based programming environment and assessment management system custom-made for the course. The system was conceived, designed, and implemented by students of the course, which provided the glue for building a sustainable and scalable community of learners, educators, and student software developers. This experience report describes the pedagogic approach, the course structure, and software system to accommodate the needs of this community. A qualitative and quantitative analysis of the impact of the course over the last four years provides evidence for its efficacy. We hope that this report serves as inspiration for similar large-scale pedagogic efforts that bring learners, educators, and student developers together to form sustainable and scalable learning communities.