In 2004, Boston Public Schools reported that more than 8% of its students dropped out of school that year. The city faced a crisis. Thousands of students were failing to earn a high-school diploma, a necessary credential for entrance into postsecondary education and/or the twenty-first century workforce. Factors driving students' decisions to leave school were closely intertwined with the more pervasive problems of poverty in urban neighborhoods. The challenge seemed overwhelming. Yet, it was at this moment that the work of the Youth Transitions Task Force was beginning to coalesce, emerging as a source for advocacy and action through the district. YTTF was launched as a cross-sector coalition--composed of school leaders, community-based organizations, and local foundations--to advance innovations in education policy and practice and support greater numbers of Boston youth in completing a high school diploma. They mobilized constituents on issues affecting disconnected and at-risk youth and influenced decision-making at the state and local level. Looking back over a decade of work, one data point stands out: in 2014, Boston's dropout rate was 3.8%. Using a collective impact framework to examine how shared ownership of complex social issues can lead to large-scale change, this case study from the Rennie Center for Education Research & Policy documents the work of YTTF in building a city-wide, cross-sector coalition to support dropout prevention and recovery in Boston. To do so, the Rennie Center completed interviews with more than a dozen YTTF members and stakeholders. The resulting case study, titled "Youth Transitions Task Force: A Ten-Year Retrospective," highlights YTTF's key accomplishments and the challenges that lie ahead. A list of case study respondents is appended.