This is an interesting topic to raise, Gemma.  I have had a few questions from schools (in my role).   I found this guide which I thought was quite helpful https://www.assistancedogs.org.uk/app/uploads/2023/08/ADUK-Quick-Guide-to-Assistance-Dogs-in-Schools.pdf .

Thank you Melinda, that is a really helpful document.

We have had an extremely positive experience of having an assistance dog in one of our secondary schools in Warwickshire, but it was over ten years ago. The charity set up all the systems, advised on risk assessments and policies needed. Our H&S were supportive and advised the Gov. Board.  A local volunteer came in during the school day to take the day out for a walk / toileting!