While K-12 online education and cyber charter schools have existed for decades, the COVID-19 pandemic of 2020 compelled every professor and teacher globally to participate in this mode of instruction. Four years after the pandemic, many brick-and-mortar K-12 schools have retained cyber or online classes within the curriculum to offer students more flexibility and wider course availability. This study specifically examines the impact of online instruction on K-12 teachers regarding lesson planning, preparation, classroom management, and relationships with students. The research occurred at a large northeastern public school district and included mostly middle and high school teachers. The data collection through surveys and interviews included teacher demographics and open-ended questions about teacher experiences with online instruction before and after the pandemic. This study found that losing community and relationships in the online environment posed the greatest challenge for K-12 teachers. At the same time, the storage and organization of classroom materials offered some of the greatest benefits. Teachers suggested that school leaders provide more intensive professional development for collaboration with colleagues who instruct online and techniques for using technology tools. However, more research is needed in the areas of effective online instructional practices and an exploration of in-service and pre-service certification programs to ensure teachers are prepared for this type of instruction. [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.]