Understanding this is hypothetical... And All that may be well and good.
However, if something happens to one of them during the night there will be no one to hear them and there to help them.
When I first joined this site there was a girl who had gliders in her class room, for some reason they didn't have access one weekend to feed or check on them.
One glider got it's foot snagged on some thread and was hanging from one toe for who knows how long before they found it monday morning. Then they didn't have funds to take it a vet for immediate care.
Was quite a sad thing to read, and while it's not a common thing for gliders to be kept at a school this is one good reason they really shouldn't be. Gliders are most active at night and I'd venture to say most accidents happen when they're active.
I know I have been woken up in the middle of the night when my male got snagged on a piece of fleece, they can and do let you know that they need help, but they need someone in the same building to be there to hear them.
It's great that your friend would pamper and spoil them but really they shouldn't be left over night in a school. They should be kept primarily at her home, and bring them to school in a bonding bag if she wants. The other thing I would worry about is janitors using cleaning products around or on the cage that could make them sick. Glider cages can have a smell to them and a well meaning janitor may want to help by using cleaning products unsafe for gliders.
Anyway just wanted to let you know there are some things to consider that you may not have thought of.