This dissertation uses a multi-case study approach to investigate teachers' use of computer science (CS) tools and pedagogical approaches in the classroom following their participation in a computer science integration professional development (PD) program. Seven teacher participants took part in a weeklong PD program and received follow up support from CS undergraduate students taking part in a service-learning course at the local university. Observations, interviews with teachers and undergraduates, and undergraduate reflections were analyzed using a constant comparative methodology to determine themes around tool use, pedagogical practice, and undergraduate roles and perceptions. Findings support that teachers' use of CS tools and resources were likely affected by multiple factors, including professional development, outside peer influences, and teachers' CS content and technical knowledge. Furthermore, teachers' use of pedagogical practices was influenced by their use of tools, resources, and background knowledge. Finally, findings indicated that the unique undergraduate support model offered benefits to both teachers and students although guidance may be necessary to provide all constituents with the most productive experiences. This dissertation provides insight into the factors that influence teachers who are new to CS education the ability to implement CS learning opportunities into their classrooms. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]