This brief is one in a series aimed at providing K-12 education decision makers and advocates with an evidence base to ground discussions about how to best serve students during and following the novel coronavirus pandemic. The brief breaks down the issue into three points: (1) Missing school negatively affects academic and socioemotional outcomes for all students, but the impacts are largest for low-performing, low-income, and English learner students; (2) The biggest drivers of absenteeism are transportation challenges, student health, school climate, mobility, and poverty--for individual students and for communities; and (3) The virtual learning environment, increased physical and mental health concerns, and reduced transportation access associated with the COVID-19 pandemic have exacerbated the problems that cause student absences. Based on these points, the brief provides three tiers of ten strategies to consider and three strategies to avoid.