- You should have gone at break-time/lunchtime.
- I'm not surprised; you've just drunk a litre of water/Red Bull/Irn Bru/coffee/Smoothie/etc, etc...
- Can't you wait?
- Not again.
At my school, students are only allowed out of lessons if they are in possession of the teacher's "yellow card". Any child wandering the corridors not carrying the card will be stopped and challenged.
My yellow card is stuck on the wall near the door.
If a child needs the toilet, they don't need to ask. They get up, take the card, go to the toilet, come back, put the card back on the wall, and return to their seat.
Occasionally, a child will take advantage of the system.
If I suspect this I put a note in their book with the time they left and then I'll write the time they came back.
It's all about trust.