The COVID-19 pandemic brought unprecedented changes to education, influencing both teachers and learners. As a result of the global health crisis, teachers adapted their teaching methods to accommodate their students. The purpose of this qualitative phenomenological study was to explore the COVID-19 pandemic challenges on the K-12 education sector from the lens of the classroom teacher and the factors that influenced their teaching efficacy following the forced 2020 school shutdowns. Furthermore, this study sought to understand the factors influencing teaching efficacy during the COVID-19 global health pandemic. This study involved a targeted population of public school teachers at elementary, middle, and high school levels from a single school district in middle Tennessee who taught at least one school year before the start of the pandemic and during the school year following the 2020 COVID-19 pandemic school shutdowns. Through semi-structured focus group interviews with 10 participants, I sought to identify how teachers perceived challenges in teaching, learning, and teaching efficacy during the COVID-19 pandemic. During the analysis phase of narrative responses from focus group interviews, themes based on each interview question emerged consistently with the literature review. Transitions in instructional delivery and student engagement during the pandemic were cited as challenges in teaching and learning. Teacher mindset and teacher support were found to be influential factors for teaching efficacy during the pandemic. This study contributed to the growing research on the COVID-19 pandemic concerning education. [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.]