Just popped back into this. ssflower I really feel for you as your mind must be racing as to what else the staff there fail to notice. As someone has said, this is almost impossible to prove.
My reason for the first, rather succint comment about changing schools is simply down to my own experience. DS had issues at his infant school, I complained and everyone closed ranks around me, I believed the gumpf I was told but was still unsure so I volunteered as a helper for a day a week. It was awful, not one adult spoke to me (I thought I had left the playground behind ) and when I spoke to the head regarding DS's problems making friends, she told me she had watched him the previous day playing football with all his new mates. I had been there that day and had to watch as he had spent the lunch hour on his own on a bench . She was bare faced lying to me. I didn't know which way to turn and felt like it was too much hassle for him and we stuck with it. 6 awful years later he is in a brilliant place personally now .
When DD came to school age, I was a lot wiser and on the ball and got her into a school that I am completely happy with. In fact, she has had a couple of accidents of the smelly nature, and the TA has just given me a little bag with soiled clothes in, and a note requesting their spare clothes back, washed. It is absolutely within their remit. I agree children need to be toilet trained when they start school, but you have to allow for the fact that small children have accidents, particularily when in new surroundings and around unfamilliar adults.
Seriously, try to change schools, it would have been better all round for us if we had. It's taken me years to shake off the reputation as a 'difficult mum'. I've recently starting working very closely with the sister school and learnt that DS actually came to that school with that label on him. Abhorrent. (sp?)