Question Author
I'm not sure what the mum intends to do with the child during her evening shift. The information I have been given doesn't specify if she is employed by an agency or by the school itself which is why I didn't know whether she could be classed as a member of staff, and it also doesn't say if the child is at another school, just that she went to a primary somewhere near the high school and that the mum was able to get her in the gap between the dinner shift and evening shift.
There's hasn't be an awful lot of extra information provided which is why I was having trouble with the question, if I knew some of the extra points that have been raised in this thread alone I'd have an easier time creating an argument.