Silence is golden is a classroom mantra repeated the world over.
But, imagine a classroom being shaken by a sound louder than a rock concert; a sound as loud as a thunderclap or a chainsaw.
Welcome to the classroom of Annalisa Flanagan - the owner of the world's loudest shout.
The Belfast primary school teacher bellowed her way into the world record books in 1994 with a thunderous bellow of the word (what else?) 'quiet!'.
The shout clocked up an earth-shattering 121.7 decibels, setting a world record and potentially damaging the hearing of anyone within earshot.
