It has come from my experience that students with Autism love to have structure in their day. Whether it be having the same breakfast, going to their locker everyday before 3rd period or not. This structure adds stability to their day and helps make their day go smooth.
I have also seen the opposite effect of a unstructured schedule that severely hurt the student. If there is a substitute teacher in math class the student will lose focus instantly and I have found that if you avoid that situation entirely, the students day is not as disturbed.