They are not allowed to make you come to clean up your child/change a pull up or whatever as that is discrimination.
It falls under the Disability Discrimination Act
"Education providers have an obligation to meet the needs of children with delayed personal development in the same way as they would meet the individual needs of children with delayed language, or any other kind of delayed development. Children should not be excluded from normal pre-school activities solely because of incontinence. "
"Schools and settings should consider the following issues:
Health and Safety
Schools and all other settings registered to provide education will already have Hygiene or Infection Control policies as part of their Health and Safety policy. This is a necessary statement of the procedures the setting/school will follow in case a child accidentally wets or soils him/herself, or is sick while on the premises. The same precautions will apply for nappy changing."
"Asking parents of a child to come and change a child is likely to be a direct contravention of the DDA, and leaving a child in a soiled nappy for any length of time pending the return of the parent is a form of abuse"
"Child Protection
The normal process of changing a nappy should not raise child protection concerns, and there are no regulations that indicate that a second member of staff must be available to supervise the nappy changing process to ensure that abuse does not take place. Few setting/schools will have the staffing resources to provide two members of staff for nappy changing and CRB checks are carried out to ensure the safety of children with staff employed in childcare and education settings. If there is known risk of false allegation by a child then a single practitioner should not undertake nappy changing. A student on placement should not change a nappy unsupervised. "