Art-making for Students with Cognitive Disabilities

I am doing an independent study in art for students with disabilities, where I have an internship working with individuals with low functioning autism. These students are all extremely mentally handicapped, and are also lacking motor skills. The lessons that the art teacher does with the students focuses on different art processes rather than conceptual ideas. Most of the projects are themed for the seasons. He uses stencils and masking techniques in all of the projects. It is definitely apparent that the students are working on these skills, and that the skill level is appropriate for them. Here at SUNY New Paltz, we learn as art educators to never teach like this. I am wondering how a different approach to teaching art would be with this population, when cognitively based lessons are out of the question. My advisor told me that the teacher should be more concentrated on using Tim Lefen's A.R.T. approach, which involves the student telling the teacher where they want the brush strokes to go in order to create their artwork. I feel that this approach is more for people who are physically disabled, but are higher functioning mentally. I wonder if anyone has any input on this topic.