Purpose: Although there is a strong evidence base supporting the use of augmentative and alternative communication (AAC) in school settings, the research-to-practice gap in this area remains a concern. Few studies have examined how AAC systems are implemented in school settings and whether these systems adequately promote communicative competence for students with complex communication needs. The aim of this case study was to better understand the ways in which elementary-age students with complex communication needs used AAC throughout daily routines. Method: Observations of five students, four receiving services under the category of autism and one under intellectual disability, in school settings were conducted to document the communication function, type of AAC systems used, and the times and activities during which AAC systems were accessible. In addition, supplemental interviews were conducted to understand the rationale for AAC implementation from the perspective of the special education teacher and speech-language pathologist. Results: Overall, findings from the observations and interviews indicated that a variety of AAC modes were utilized. Interactions represented a range of communicative functions, with the exception of social closeness, and were primarily observed during academic activities. However, there were some discrepancies between observations and interview data. Conclusions: Although these findings provide insight into how students with complex communication needs may use AAC in elementary school settings, more research is needed to explore AAC use across a range of students, classrooms, and schools. We present specific future research directions, along with implications and recommendations for AAC teams and researchers.