In March 2020, most schools in the United States closed their doors and transitioned to distance learning in an effort to contain COVID-19. During the transition a significant number of students did not fully engage in these learning opportunities due to resource or other constraints. An urgent question for schools around the nation is how much did the pandemic impact student academic and social-emotional development. This paper uses administrative panel data from California to approximate the impact of the pandemic by analyzing how absenteeism affects student outcomes. We show wide variation in absenteeism impacts on cognitive and social-emotional outcomes by grade and subgroup, as well as the cumulative effect of different degrees of absence. Student outcomes generally suffer more from absenteeism in mathematics than in ELA. Negative effects are larger in middle and high school. Absences also negatively affect social-emotional development, with slight differences across constructs. Our results add to the emerging literature on the impact of COVID-19 and highlight the need for student academic and social-emotional support to make up for lost gains.