New York City's Mayor Michael Bloomberg and school's Chancellor Joel Klein made the creation of new schools an essential part of their Children First reform policy. In September 2002, 13 high schools opened replacing the lowest performing large high schools throughout the City. As of 2010, more than 400 new district and charter schools are in operation across the City. High schools involved this initiative have a variety of themes and philosophies yet all new school proposals required a "lead partner" in the co-creation, design and operation of these schools. Lead Partnership was defined in the Department of Education literature to include roles and responsibilities in four key areas: leadership and decision making, governance, day-to-day operations, programming and curriculum development. This dissertation illustrates the characteristics of sustainable partnerships. I interviewed six principals who started schools in the first two years of the initiative. I also reviewed their original proposals. The criteria for participation in the study included principals of schools at a "midlife" stage of development defined as the period of operation following the support of an intermediary organization, past the four-year Gates Foundation grant funding cycle and "fully operational"--including all ninth through twelfth grades and having graduated at least one class. In theory, private-public partnerships are meant to bring innovation, resources and alternative models of leadership into schools. The findings suggest that all schools benefited from additional resources, funding and professional expertise attained through these partnerships. There was however varying degrees of involvement in the four key areas of operations that define lead partners. A Continuum of Partnership Relationships was developed arranging these schools into four categories: Institutionalized; Intermittent; Participatory Vendor and Uninvolved partnerships. Further analysis revealed three common characteristics for building and maintaining sustainable partnerships. These included partners having: a vested interest; close proximity to the school; and capacity for educational competencies. Three factors also contribute to the challenge of defining and executing roles and responsibilities leading to sustainable relationships. These included going to scale with thematic programs, the expected length of the partnership, and the accountability of the partner to the academic success of the school. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]