Policymakers and educational leaders across state and federal agencies have invested considerable effort in identifying how schools can both mitigate and exacerbate student absenteeism. Despite extensive research into school-level characteristics and programs, there remains a notable gap in understanding the impact of classroom-level factors on absenteeism. This study investigates how classmates' absences impact student absenteeism in four Texas school districts, analyzing both in-person and virtual contexts. Using a novel approach that accounts for day-to-day attendance variation, findings indicate that in-person absenteeism among peers significantly increases a student's absenteeism, with effects lasting up to three days, regardless of achievement levels. However, virtual absenteeism showed no similar impact, highlighting distinct absenteeism dynamics in virtual environments. Amid COVID-19 disruptions, this underscores the need for interventions addressing absenteeism across varied learning settings, offering insights for policymakers and educators in navigating the challenges of both physical and virtual classroom dynamics.