Background: Students with disabilities are encouraged to achieve rigorous academic standards in science to enhance their understanding of the natural world, acquire life skills and prepare for their successful careers. Augmented reality (AR) enriches the physical world experiences benefiting all students, including those with Intellectual Disabilities (ID). Objectives: This study investigated the effectiveness of immersive AR in improving learning outcomes on the states of water among six students with ID. Methods: Two different approaches were implemented using AR glasses--a structured inquiry method rooted in constructivism was used with three students, while a systematic instruction grounded in behaviourism was used with the remaining students. Results and Conclusions: The results showed a functional relationship between students' correct responses (dependent variable) and the type of intervention (independent variable). Learning outcomes were improved for all students, and those who followed inquiry learning developed inquiry skills. Regardless of the type of the intervention, the follow-up phase revealed that the six students retained their learning gains at a high level and generalised the new content. Evaluating students' experience, all of them reported that they enjoyed the AR intervention, and that immersive AR contributed to their understanding of Physics terminology and inquiry skills. Implications for Practice By offering an inquiry-based AR immersive environment, students with ID are more likely to overcome the challenges of inclusive science settings and develop science literacy.