While the physical environment is widely understood as being a critical consideration for children with autism spectrum disorder (ASD), limited research is available to guide the design for these specialized classrooms. A two-phase case study explored teacher's perceptions of the classroom experience at a state-funded charter elementary school for children with the primary diagnosis of ASD. The first phase occurred prior to the COVID-19 pandemic (2017-2018) and the second phase occurred during the crux of the pandemic (2020-2021). In this qualitative inquiry, three questions are explored: (1) How do teachers, therapists, and administration perceive the influence of the classroom environment on elementary school children with ASD? (2) How are teachers adapting their physical classroom environments to meet the unique needs of students with ASD? (3) How do teachers perceive the influence of the COVID pandemic on the learning environment? Methods utilized were face-to-face interviews, photo-elicitation interviews through Zoom, and classroom observations. Nine teachers, five school therapists, and the school principal participated in the study. Findings identify adaptations with interior design considerations: auditory, visual, and tactile sensory processing; artificial and natural lighting; interacting with furniture, fixtures & equipment; classroom definition/organization, space planning, crowding, storage, escape space, and circulation; health, safety, and security; and flexibility/adaptability for individual student needs. Teachers, therapists, and administration all feel the physical classroom influences children with ASD and requires careful consideration. Teachers need to adapt their classroom environments to meet their students' unique needs to ensure the environment is affording the learning process. It was also found that student grade level and function had an impact on the students' ability to cope with environmental stressors in the classroom. Adapting to COVID restrictions had both positive and negative outcomes. The study concludes with practical considerations for ASD classroom design. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]