In the spring of 2020, when faced with emergency school closures teachers had to switch from teaching face-to-face in brick-and-mortar classrooms to virtual meetings and online classrooms. To make changes quickly, teachers used the technology skills they already practiced and acquired others to engage and instruct their students online. This phenomenological exploratory sequential mixed methods study sought to understand how teachers adapted their use of technology in the classroom during unexpected long-term school closures and remote teaching resulting from the COVID-19 pandemic through the lens of growth mindset (Dweck, 2007). Participants in this research are from GATE Magnet, Dual Immersion Mandarin, Title 1, and non-Title 1 elementary K-6 schools in a unified school district in Southern California. Qualitative data was collected from a small convenient sample (n=9) using phenomenology methods. Qualitative data analysis used open and axile coding to group commonalities to generate themes. Common themes guided the development of a survey to collect quantitative data from a larger sample (n=40). Quantitative data determined the generalizability of the identified themes. The findings revealed that amidst chaos, teachers felt a call to duty. Teachers were determined to persevere, problem-solve, and develop methods to educate their students, impromptu, with little or no guidance. They organized schedules for online learning, held virtual class meetings with their students, created and implemented online teaching materials, assignments, and projects to continue and foster the academic success of their students while experiencing unprecedented challenges. Their survival tactic was to simplify and streamline course content as they pivoted their practices to prepare for remote teaching in the weeks ahead. Their determination and sense of responsibility to themselves and the success of their students motivated their efforts while utilizing a growth mindset to stay the course. The word "responserverance" (responsibility + perseverance) describes teachers' response to the complex challenges of long-term school closures. [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.]