School absenteeism is a significant social and public health problem. However, existing prevalence rates are often not representative due to biased assessment processes at schools. The present study assessed school absenteeism in Germany using a nationwide online self-report survey. Although our definition of school absenteeism was more conservative than in previous studies, nearly 9 % of the 1359 high school students reported school absenteeism within the past 7 days. Absent students lived less often with both parents, were on average of lower socioeconomic status, and reported more emotional problems, behavioral problems and less prosocial behavior than attending students. Being an indicator of a wide variety of problems in children and adolescents, school absenteeism deserves much more attention. Future directions for research and implications for prevention and intervention programs are discussed.