Recent policies and initiatives emphasized the importance of helping all students acquire Computer Science (CS) knowledge and develop Computational Thinking (CT). This study investigated the impact of a school-university partnership model on school students' CT development in the context of an after-school program. This study also examined the ways in which college CS undergraduates supported practicing teachers in the field, both through teaching practices and material development. The overall purpose of this work is to link CS undergraduates' practices from the designed partnership model to in-class support for teachers and subsequent student outcomes. Participants included 65 school students in grades four to six who voluntarily participated in the nine-week after-school program, as well as six CS undergraduates and one practicing teacher who designed and implemented the program. Data were collected from multiple sources, including after-school program observations, undergraduate reflections, CS case reports, CS content assessments, programming products, design journals, and a teacher interview. Results indicated that CS undergraduates actively sequenced, facilitated, and co-led a set of progressive, cohesive, meaningful, and relevant CS lessons with sound pedagogical strategies and age-appropriate CT tools and activities. School students' learning progress was also guided and built upon several formative and project-based assessments. Further, results indicated that the school-university partnership program positively influenced student learning of CS concepts, practices, and perspectives. Findings from this work can help provide guidelines for the design and implementation of effective partnership programs that help broaden participation in computing, with attention to the ways in which field experience and CS undergraduates can help support CS education in local communities. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]