California allocates $550 million to expanded learning through After School Education and Safety (ASES) state grants, and $140 million of federal money in 21st Century Community Learning Center grants each year; more than all other states combined. Much variability exists in program quality, and research has identified mixed results as to the value of these programs. The purpose of this study was to identify (a) Quality Self-Assessment Tool (QSAT) elements and Learning in Afterschool and Summer (LIAS) principles frontline implementers and technical assistance providers perceive as most important or essential to developing, executing, and sustaining a high quality program and (b) explore the value and impact of using the QSAT and LIAS principles tool to improve and sustain program quality. A mixed methods design included both quantitative and qualitative data. Fifty Q-sorts, using Q Methodology, explored participants' perceived level of importance regarding statement elements related to developing and sustaining a high quality afterschool program. Findings revealed that participants consistently ranked four statements derived from the LIAS principles as most important for developing a high quality afterschool program. These statements described programs that engaged students in active, collaborative, meaningful learning activities that expanded horizons. Participants indicated four elements as critical to operating an afterschool program of quality: well defined, hands-on, student-centered activities incorporating academics, youth development and recreation; students and staff with a strong sense of ownership and belonging; active learning experiences; and meaningful learning experiences. Twelve individual interviews with frontline afterschool program implementers explored the use of self-assessment, most specifically the use of the QSAT and LIAS principles tool, to improve and sustain program quality. Six themes emerged relative to what participants identified as a need to move their programs to highest quality: money, training, staff, leadership, systems for continuous improvement, and support from stakeholders. Four themes emerged as facilitators to improving and sustaining an afterschool program of quality: leadership, establishing a vision and setting goals, staffing---recruiting, hiring, training and retaining quality staff who develop positive relationships, and support; while money or level of funding was the primary theme perceived as a barrier. [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.]