Ham it works for YOU. It wouldn't work for my dc. I think Goldmandra's post is spot on.
Both my dc are further terrorised by firm tones when already stressed, their fear levels go through the roof, after four years of daily firm routine at school, my ds was still no closer to coping, was regressing and becoming non verbal, self harming severely. I had to remove him in the end, it truly was a choice between that or losing him. Following your reasoning, the routine and structure of school should surely be a suitable environment for such children but for many they are totally unable to cope there, this is a well documented fact.
Once my dd in particular has tipped over it is impossible to bring her back, nothing works but to remove her to a place of safety, no amount of lists or routine etc. Once she's gone she's gone. Doesn't matter where she is, public or otherwise, she cannot be reached till she is back down.
I am glad your way worked for you, I really am but I cannot agree that it will work for everyone. In your first post you say "you HAVE to teach them" as though this is possible for everyone. It isn't, many times all you can do is keep trying and minimise the fall out, it may be that some triggers are so strong they will never overcome them.
Out of interest you say your family members have "severe autism". This is a very different thing to more higher functioning people with autism who in their way can often be more challenging.