Using school-month-level learning mode data and high school completion rates across three school years from 429 Wisconsin public high schools, this study examines the impact of disruptions to in-person instruction during the COVID-19 pandemic on high school completion rates, with a focus on socioeconomic disparities. Findings reveal that a longer time in virtual or hybrid learning mode in 2020-21 decreases overall school completion rates and increases the within-school gap in completion rates between economically disadvantaged and non-disadvantaged students. This study provides further evidence of the unequal impact of the pandemic and calls for initiatives to support disadvantaged students during school disruptions.