Students in primary grades are rarely absent without parental knowledge. Many parents don't really think too much of having a young student miss school for a family event, or even just parental convenience. For many families the impact of occasional absences may not be significant, but for students who are at risk of failure -- whether because of poverty, English language barriers, or unstable family situations -- absences even in early grades can have a cumulative impact upon academic performance. A seminal paper on this topic, Present, Engaged, and Accounted For: The Critical Importance of Addressing Chronic Absence in the Early Grades, from the National Center for Children in Poverty, found that for students in ninth grade, missing 20 percent of the school year is a better predictor of dropping out than test scores.
Furthermore, students with chronic or frequent illness may have excused absences, but unless efforts are made to continue their schoolwork or to make up missed work, something that is often difficult or impossible in less affluent school districts, the fact that these absences may be unavoidable does not diminish their impact upon future performance and graduation.