I know of children (with clear medical issues, well documented to the school, toileting care plans written into statements etc) who have been left soiled (child not wearing nappies/pull ups as trained if reminded/prompted/taken at regular intervals) - literally soaked through with wee and poo - for a good part of the day.
teachers and TAs who deny all knowledge that there has been an accident (despite olfactory evidence to the contrary) - children who end up with welts and weals from acidic poo drying onto their skin, and being left there all day.
this happens too - clear neglect on the part of anyone at the school, and complete failure of duty of care.
all because 'the child should be toilet trained' or 'we can't always be on hand to deal with every little thing'.
I think part of the rise in children starting school not toilet trained is down to the rise in SN - dyspraxia, sensory issues, ASDs are on massively on the rise, and this is showing up more with a higher proportion of children (whether dx'd at that point or not) not 'ready' to start school.