Researchers have shown that the practice of online learning throughout all levels of education has increased rapidly since the early 1900s (Hu et al., 2019). With the recent and ongoing Coronavirus pandemic, many learning institutions have shifted to full or partial online learning. (Lily et al., 2020; Sharfstein & Morphew, 2020; Subramanian et al., 2020). With this immediate and abrupt shift to online learning, many education leaders, teachers, parents, and even students became concerned about how learning online would affect the student's overall success in education (Sharfstein & Morphew, 2020). Therefore, the problem addressed by this study was the decrease in academic performance and student engagement related to online learning in the K-12 educational setting, as reported by numerous studies examining online learning in K-12 education. Furthermore, the overall purpose of this qualitative case study served to examine high school student perceptions of online learning and its impact on the academic achievement and student engagement of K-12 online learners. A sample size of 20 high school students in grades 10-12 enrolled in online courses during the 2020-2021 school year were chosen to participate in this study. Data related to student perceptions of their online learning experiences and the impact on their overall engagement and achievement was collected via semi-structured interviews and online questionnaires, which was highly effective for data triangulation during the analysis process. The data from this study were analyzed using a qualitative data analysis software (NVivo). Overall, in this study are the residual hopes that these findings will influence educational leaders and teachers to focus on the areas students feel are vital to their success in the online learning environment. [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.]