I have used this program with an autistic girl. She could speak but didn't communicate. She repeated the same phrase over and over again. She also had to line up everything and wipe things off before moving on to another activity. At 9 years of age she couldn't read or write, although she did know her alphabet sounds. She had rage issues as well. I had to be very physical with her at first and take her by the hand to perform the exercises. Fortunately she trusted me and would allow it. It has been a year and a half and she is communicating with peers and adults. She reads at a 2nd grade level and is approaching 3rd grade. Her rages have subsided, although she still is having some fear issues. She can write, although not yet at grade level. Her math skills are not at grade level yet, either. However, even if she makes no more progress than this, then she will be able to function in society.
I have wanted to try this program on more severe autistic children, but to be honest, I don't have the energy right now. I feel you would have to be physical and do the exercises for them at first. Also, these kids would have to trust you, and that would take time, which is something I don't have a lot of. A parent is the perfect person to do this program with a child because the trust issues are there.