I'm a secondary school welfare/receptionist, and we call them runners. It's one day in year 8, one day out of 7 school years. I think Y8 are chosen as in the great scheme of things it's the least important year in terms of being new or getting ready for GCSE etc.
Year head vetoes any naughty kids, and it's seen as a big responsibility and an important job, which it's is.
The kids love it, they get to go on breaks a few minutes early, they can eat and drink at the desk they sit at, they get to go into parts of the school that would usually be out of bounds to them, and they usually get a hot chocolate and a biscuit at some point in the day from us.
They are expected to do h/w or read when not busy. We would not expect them do anything yucky.
We could not manage without them tbh. We are school of 1200 with 150 staff. We get dozens of visitors everyday who have to be "delivered". Parents regularly decide in the middle of the day that their kids need to leave for GP appts etc without telling the child in the morning so we have to send a runner to collect them when the parent arrives wanting their kid NOW. Kids forget kits/homework/lunch/violin and facebookwe have to deliver those - literally 30 to 40 times a day.
If I was running around delivering things for disorganised kids/parents, then I wouldn't have time to take care of the constant stream of kids with period pains, headaches, cut knees etc etc.
It's looked at a learning experience and a privilege for the students and they really enjoy it (apart from the odd lazy/grumpy one!).