Adherence to sustainable development in higher education rests on the assessment of students’ academic attainment, especially during unexpected environmental changes, such as the sudden move from face-to-face to online courses during the recent pandemic. Most studies devoted to this issue have compared students’ performance online with that of face-to-face courses before the pandemic, tallying together a variety of courses, often from specific disciplines. Besides their mixed results and generality, such studies do not address the issue of students’ adjustment to the post-pandemic learning environment. The present retrospective case study offered a simple evidence-based model for educators to measure the relationship between environmental changes and students’ behavior for self-reflection and adjustment. It examined students’ academic attainment (as measured by grades) within a broader timeframe, including courses taught by the same instructors face-to-face before and after the pandemic and online during the pandemic. Specific courses of the general education curriculum were selected to include a broad spectrum of students. The study then assessed whether students’ activities before, during, and after the pandemic predicted summative assessment performance (i.e., final exam grades) differently. In this study, performance differences were recorded, usually in favor of post-pandemic face-to-face classes. Midterm examinations were the best predictors of final exam grades irrespective of the modality of instruction and timeframe. Implications and applications of the methodology used and the results obtained were considered.