Garway Primary School have a system where they blow a whistle 5 minutes before the end of each break or lunch time as a signal for the children to get themselves a drink and to go to the toilet if necessary. This means that they are all ready to start when the lessons begin!

If any of the children need to refill their water bottles during lessons, they are able to but must wait until a time when the teacher is not speaking!

Sounds like a plan to me!
 

Short of overalls/aprons for messy jobs? Take one good quality plastic carrier bag - hold it by the handles and cut the bottom off! Now place over the head of a suitable child to hand (and pull down)and hey presto - a coverall! Cheap, disposable and readily available.
 

A local school have a novel way of procuring their supplies of toilet rolls!

At their Christmas disco, entry fee is 50p plus a toilet roll! This way the school saves pounds and the children have top quality loo roll!

This could be used for any event and when stocks are dwindling, have a 'wear what you like day' - you've guessed it - the contribution is one loo roll!