The increased availability of low-cost, standalone and immersive virtual reality (VR) can facilitate adoption in autism education. An immersive VR implementation of the individual work system (IWS) from the TEACCH® approach has the potential to be a safe and predictable environment for autistic learners with or without intellectual disability. This study is a multi-site usability and safety trial examining an immersive VR implementation of the IWS co-designed with autistic pupils and their teachers from three educational centers in the UK, Spain, and Turkey. Twenty-one autistic students aged between 6 and 17 years were involved in the study, six of whom had an intellectual disability. The students tested a total of 164 customized tasks. All participants were able to finish all the tasks. No significant safety issues were identified. The student's average score on the SUS Usability Scale was 85.36 points. A linear regression analysis showed that autistic children with intellectual disability scored significantly lower on feasibility than children without intellectual disability (p < 0.01) across all locations. This study concluded that an immersive VR-IWS proved usable and safe for the 21 students. However, our findings highlight the need for further adaptations and further research on those with an intellectual disability before recommending universal use. Our findings also have implications for game design for learners with special educational needs.