The number of students using augmentative and alternative communication (AAC) systems in mainstream schools has increased in recent years, in line with the principles of inclusive education. Teacher perceptions of AAC significantly influence school practices and the overall effectiveness of these systems as a tool for communication and inclusion, which can enhance the presence, progress, and participation of students who use it. The present study seeks to analyze these perceptions and find out if aspects such as training or previous experience influence them. To this end, an analysis is conducted using the Spanish Questionnaire “Perceptions on the Inclusion of Students who use AAC in mainstream classrooms (PSIASAAC)” with a sample of 122 teachers from the Spanish Autonomous Community of Valencia. The results show favorable perceptions towards the inclusion of students who use AAC. However, there are notable differences between teachers with and without training and/or professional experience with AAC. The findings align with those of several previous studies conducted in different contexts. This leads us to believe that while there are generally positive perceptions of students who use AAC systems, it is important to intensify efforts in the initial and ongoing training of teachers. It is also crucial to share successful practical experiences demonstrating how the use of AAC systems contributes to improving the educational inclusion of the students who use it.