Several studies have tried to estimate the effects of the COVID-19 pandemic on student learning and the learning differences between social groups. Few studies have looked at the effects on other aspects of students’ educational achievement, especially grades. Institutionally, grades are essential for evaluating students’ ability, for tracking, for graduation, and as a signal for the labor market. However, grades are subject to many non-performance-based factors, e.g., students’ characteristics such as gender or social origin. Based on previous research and theoretical arguments, we expected grades during school closures to be less correlated with cognitive competencies and higher correlated with social origin than previous cohorts. We analyzed the effect of the pandemic on students’ grades in mathematics and German at the end of Grade 8. The pandemic can be seen as a natural experiment that can be exploited when analyzing two cohorts of the German National Educational Panel Study. The grades of the younger cohort (n = 4,069 students) who were in Grade 8 during the pandemic (2020) were compared to the grades of the older cohort (n = 6,861 students in 2014). Our results show no systematic increase in educational inequality based on the social origin of students. However, students in the treatment group reported higher grades which might be a result of pro-social grading by teachers.