Do as you're told!

This sign was in the waiting room of the hospital today. My taking of the picture attracted attention to it and some of the people in the waiting room started to reminisce about putting chewing gum under desks at school!
I was at the hospital with mum. She's started a course of treatment. We spoke with such a nice consultant - she held mum's hand and explained things carefully, clearly and with compassion. She even gave her a big hug when she got upset. Once again I am SOOOOOOOO thankful for the NHS and amazing staff. I am horrified at what seems to be happening to it in England and Wales.
I did wonder if those inclined to put chewing gum under the seat would routinely use the word "refrain".