In 2020, the COVID-19 pandemic necessitated a shift to remote work-from-home (WFH) setups, including in the education sector. This transition had a significant impact on the interaction between students and instructors. To address this, our study aims to investigate the effects of the sudden transition to online learning on teaching methodology and to propose improvements to enhance its quality. We have developed a scoring system to evaluate teaching quality in the post-COVID-19 world. The scoring function incorporates various metrics, including students’ performance, sentiment towards the course (course material, teaching method, communication, etc.), feedback scores for weekly lectures, and students’ retention scores for recorded/live lecture videos. Following the Lean Six Sigma (LSS) procedure (Define, Measure, Analyze, Improve, and Control—DMAIC), we assessed the overall quality of online courses. The undergraduate courses demonstrated an increase in overall score from 86.67% during the online transition to 90.0% after implementing the suggested improvements. For graduate courses, the initial face-to-face lecture score was 55.81%, which dropped to 50.28% during the first online transition. However, after a year, the score improved to 61.59%, indicating successful improvement efforts. Upon careful analysis of the data, this paper provides suggestions to enhance students’ online learning experience during situations similar to the COVID-19 pandemic. The outcomes of the study aim to improve the quality of online learning experiences for students.