Studies consistently show associations between school absences and academic achievement. However, questions remain about whether this link depends on the reason for children's absence. Using a sample of the Scottish Longitudinal Study (n = 4,419), we investigated whether the association between school absenteeism and achievement in high-stakes exams at the end of compulsory and postcompulsory schooling varies with the reason for absence. In line with previous research, our findings show that overall absences are negatively associated with academic achievement at both school stages. Likewise, all forms of absences (truancy, sickness absence, exceptional domestic circumstances, and family holidays) are negatively associated with achievement at the end of compulsory and postcompulsory schooling. First difference regressions confirm these negative associations, except for family holidays. These findings suggest that, in addition to lost instruction, other mechanisms such as behavioral, health-related, and psychosocial pathways may account for the association between absenteeism and achievement. The findings have implications for designing tailored absenteeism interventions to improve pupils' academic achievement.