The COVID-19 pandemic has radically changed and disrupted education; colleges and universities have closed their campuses, and many have shifted to online courses. In the pre-pandemic era, online classes were associated with several benefits and challenges, and the pandemic might have brought additional benefits and obstacles. This research examined students' perceptions of online classes during the pandemic. The study looked at four aspects: perceived benefits of online classes; perceived challenges; beliefs and an overall evaluation; and potential improvements. An online questionnaire was administrated to some first- and second-year undergraduate students at a College in China. It combined a set of 23 closed-ended and open-ended questions and 342 valid and complete responses were collected. Perceived benefits included creating a digital learning community, improving students' digital learning skills, and staying connected during tough times. Challenges comprised adaptability issues due to the sudden shift to online classes, time-management issues, being distracted by social media plus technological obstacles. Regarding beliefs, students believed that a blended model that combines both classroom and online modes is necessary for the post-pandemic era. To enhance the sustainability of online classes in the post-pandemic era, a set of improvements are explored and suggested.