This constructivist multiple-case study examined the collaborative leadership practices of seven secondary and seven post-secondary leaders who participate in Ohio's Early College High School Initiative (ECHSI). The 14 educational leaders in this study partnered in an effort to respond to the access and success of traditionally underrepresented (i.e., ethnic/racial minorities, low-income, and first-generation students, and/or non-native English speaking) students in higher education. Therefore, it was proposed that relationships are essential to fulfilling the ECHSI mission, and seeks to: (a) explicate the leaders' understanding of their school-university partnership and (b) explain the relationship between Early College leaders and the Relational Leadership Theory and its components (purpose, ethics, empowerment, inclusion, and process). Collaborative leadership is a complex and dynamic process for which strong evidentiary support is required. Therefore, this dissertation applied an exploratory multiple-case study approach to analyzing seven within-case and cross-case comparisons. The foundation of this study was based on qualitative interviews, supported by a web-based survey which yielded a 100% return rate. Additionally, document analysis was used to gain a better understanding of how relationships across secondary and post-secondary educational sectors create comprehensive, seamless systems of learning. The participants explained the interplay between individual and organizational backgrounds, experiences, leadership styles, values, and goals that promoted the development of their inter-organizational relationship. In this study, three major findings uncovered that cross-sector educational programs make sense and strengthen the educational pipeline between K-12 and higher education. Secondly, the development of a collaborative working environment can be optimized through the Relational Leadership Model. Finally, true collaboration occurs through meaningful connections with open communication, trust, mutual respect, commitment, accountability, and professional knowledge and competence. Implications of findings and recommendations for future research are discussed. Notably, future research should consider the exploration school-university partnerships to build effective transitional and support services in addition to developing state-wide and national educational policies that strengthen America's educational pipeline. [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.]