Using an unbalanced panel of close to 12,000 academic records, and difference-in-differences models and event study analyses with individual fixed effects, we evaluate the impact of the COVID-19 pandemic on lower-income students' academic performance during the spring 2020 semester relative to their higher-income peers. We find a differential effect by students' pre-COVID-19 academic performance. Top-performing lower-income students experienced a decrease in both grades (5% lower) and earned credits (11% fewer) during the spring 2020 semester relative to their higher-income peers. In contrast, lower-income students in the bottom quartile of the fall 2019 cumulative GPA distribution outperformed their higher-income peers with a 9% higher spring 2020 GPA. After ruling out alternative mechanisms, we find suggestive evidence from survey data that top-performing lower-income students' lower relative performance may be driven by greater challenges with online learning and a disproportionate intake of incomplete courses relative to their higher-income peers. Among bottom-performing lower-income students, greater concerns with maintaining financial aid than their higher income peers may have led them to a higher use of the credit/no credit grade option instead of a letter grade.