School attendance problems (SAPs) are heterogeneous with respect to etiology and presentation. The long history of conceptualizing SAPs has led to a vast array of terms and definitions as well as different perspectives on the most helpful approach to classification. For educators, practitioners, researchers, and policymakers, this presents a challenge in understanding, assessing, and intervening with SAPs. This paper outlines evolution in the conceptualization of SAPs, focusing on two contemporary approaches to differentiating between them. One approach draws on the longstanding differentiation between SAP types labeled school refusal, truancy, and school withdrawal. A fourth type of SAP, labeled school exclusion, is also considered. The other approach focuses on the function of absenteeism, measured via the School Refusal Assessment Scale (SRAS). Anecdotal and scientific support for the SAP typology is presented, along with the benefits and shortcomings of the SRAS approach to differentiation. The paper offers suggestions for how to differentiate between SAPs and introduces the SNACK, a brief screening measure that permits differentiation by SAP type.