I'll just say first that my daughter's nursery is wonderful and I know that she is happy, safe and well cared for. Generally they keep her clean and change her clothes if she gets dirty. However, the ones that are potty trained are able to go to the toilet when they like during the day without help without help. My daughter has just turned 3 and can't wipe herself on her own yet. She keeps getting very sore and coming home with dirty underwear. Would you expect nursery staff to help pre-schoolers to wipe themselves or is that expecting too much?