Prevalence studies in the AAC discipline are fundamental to establishing funding, instructional, and research priorities. These data inform policy-makers on the allocation of clinical and educational services, help prioritize AAC pre-service and in-service trainings, and support AAC research grant applications. A survey study was designed to (a) provide prevalence estimates of school-age students who have highly unintelligible speech, (b) describe the demographic makeup of these students, and (c) describe their access to AAC. Rigorous web-based survey development and distribution procedures were followed. Special education administrators in New Mexico, USA were recruited to distribute the surveys to speech-language pathologists (SLPs) in their respective school districts. The majority of school districts in the state participated, and the overall SLP response rate for participating districts was high (65%). Based on the results, the best estimate indicates that approximately 1 in 89 school-age students in New Mexico has severely unintelligible speech. SLPs averaged 5.4 students per caseload with severely unintelligible speech, with 86% of SLPs providing services to at least one of these students. Only 22% of students with highly unintelligible speech had been seen by an AAC specialist. The findings highlight the substantial number of school-age students with highly unintelligible speech and the ongoing need for high quality AAC service provision for these students.