Shadow education is used not only to improve students' educational achievements but also to maintain social reproduction by advantaged families. However, little is known about the socially stratified shadow education participation during COVID-19 when the educational environment was uncertain. Using data collected before and after the COVID-19 outbreak in China, this study finds that parental education was a strong predictor of children's shadow education participation before COVID-19, but this relationship was disrupted during COVID-19. Students of parents of all educational levels equally participated in shadow education during the COVID-19 pandemic. This class-based equity in shadow education was largely explained by the substantive increase in shadow education participation among students of less-educated parents.