The literature on school absences has focused predominantly on the reasons for student truancy, or it has assessed only aggregate student absences in their effect on achievement. However, this study brings forth a new issue: the relationship between types of absences--excused versus unexcused--and school performance. With a quantitative model of educational achievement on a longitudinal multilevel data set of all second- through fourth-grade students in the Philadelphia School District from 1994 to 2000, this study disaggregated absence information to provide new insight on the attendance-achievement relationship. Specifically, a model using fixed effects with classroom-level clustering was employed to determine how the distinction among varying proportions of excused versus unexcused absences related to students' standardized test performance in reading and math. This article demonstrates that distinguishing between students with high rates of excused or unexcused absences is significant. Having a higher proportion of excused absences to total absences exhibits a positive relationship between reading and math test scores. Conversely, students with a higher proportion of unexcused absences places them at academic risk, particularly in math achievement and as early as in elementary school. Implications for policy are discussed. (Contains 3 notes, 9 tables, and 1 figure.)