The COVID-19 pandemic disrupted educational systems around the world. In this study, I sought to understand how two preservice teacher and mentor teacher pairs navigated planning and teaching during the global pandemic. Specifically, I investigated the ways in which co-planning and co-teaching practices were or were not adopted. Additionally, this study explored how preservice teachers' self-efficacy was developed and how co-planning and co-teaching practices were related to preservice teachers' self-efficacy. In this dissertation a case study methodology was employed, with data collection consisting of surveys, co-planning audio recordings, interviews, and classroom observations. The findings of this case study highlight the overwhelming workload placed on teachers while navigating in-person, virtual, and hybrid teaching during the COVID-19 pandemic. These changes placed a burden on teachers requiring revisions to instructional methods. Next, the structure and schedule of PSTs' respective schools along with the distribution of power with their mentor teacher influenced co-planning experiences for PSTs. Further, the findings revealed the co-teaching strategies of station teaching and parallel teaching fostered shared power and teacher agency, whereas the one teach one observe, and team teaching strategy diminished PSTs' agency and power. Lastly, PSTs' self-efficacy development was classified into two categories, authentic experiences, or context-specific experiences. [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.]