I remember going to school with a boy who was 11 years old.
He had autism and wore diapers all the time because he was not potty trained.
He was a very good friend of mine as well and his autism was not very severe but severe enough to where he would not grasp going to the toilet.
So he pooped his diaper when he needed and peed it as well.
When he pooped his diaper he would let me know by whispering to me that he pooped his diaper.
Then I would tell the teacher who would then tell him discretely that he could go to the nurse.
So I would walk with him to the nurses office and he would get his diaper changed in their.
He never really seemed embarrassed about having the nurse change his diapers and he seemed to enjoy it and wanted me to stay in the nurses office with him.
So I watched him get his diaper changed often.