School absenteeism (or truancy) may be a signal of an ongoing process of student attrition that eventually leads to early school leaving. This article estimates how unauthorized school absenteeism accelerates the dropout decision. In particular, the timing of the dropout decision of truants is compared with the timing of regular school attendees using administrative data with insights into wrongly specified truancy spells. We correct in a Bayesian duration model for issues on data uncertainty and show that only a Bayesian structure on the data yields insightful and consistent results. The results indicate that the risk of truants to leave school early before the end of the compulsory education age increases with as much as 37.4%.