Shelly, the OP is a longterm poster on here: we have been following her struggle to get support for her daughter for a long time. Suddenly pretending that her dd doesn't have special needs, when her family know she does, would not be helpful at all. Recognising the importance of support for a child with special needs is not the same as doom mongering!
OP, you've had some great advice on here- and good on you for getting her the help she needs and withdrawing her from that awful school! I would certainly do the following:
*get her medically checked out to make sure there is not a physical reason for her frequent soiling- having learning difficulties does not mean you cannot also have a physical problem. Soiling 8 times a day does sound a lot; I would be wondering about impacted faeces and constipation, like thisisyesterday said. I knew a little boy who was soiling frequently (and wetting himself) at the same age, and it did turn out to be impacted faeces; it can cause wetting too btw.
*try to stay as calm and non-reacting as you can (but I think you've worked this one out for yourself really). She clearly cannot help the soiling, but you need to overcome the emotional charge of the situation by modelling calm and competence. Try to pretend to yourself that you are dealing with a younger child and adopt the brisk cheerful approach you would use then.
*see if you can help her find something to soothe the soreness
*try not to draw out punishments for too long at this stage- you don't want her to focus on her failure and become stressed out about cleaning sessions
*accept that she will be going through an angry phase. This happens to most children with SN/disabilities when they realise they are different. I used to have to restrain my dd, so I know it well. Do try not to feel hurt by it, or don't allow yourself to think that there must be something dreadfully wrong morally with a child who tries to hurt people.
My dd, as it so happens, does not have learning difficulties, but she was angry because life had been unfair to her and the only person she could trust enough to take it out on was me.
Lucy has just discovered that life has been unfair to her. Eventually, she will hopefully learn to express her frustrations in a socially acceptable way, but it can take time.
I tried to concentrate on stopping dd from hurting me- I would hold her and repeat calmly, "no you will not hurt me, no I cannot let you hurt me". Eventually, dd grew out of her aggression. But I think it went all the quicker because she saw that I stayed in control.
*accept that the school probably have done a bit of damage to Lucy's confidence and it will take time for her to get over it. Dd took a couple of years to trust adults in authority after a ghastly experience of junior school. We got there in the end.
Playful parenting sounds good, it is also a way you can model being in control: somehow, that approach seems to radiate more authority than a constant stream of punishments.