My school had an established universal signal meant to garner instant silence whenever a teacher so required. It was done in kindergarten, it was done in middle and high school, and—I caustically informed my class—it was even done in staff meetings.
You, the authority figure in the room, are supposed to raise your hand. Thereafter everyone else is meant to quiet down and do the same. A successful signal is fully effective in seconds. My signals took minutes at best and would flat-out be ignored at worst. Of course, there were the poor kids who I can only compare to Hermione—their hands would shoot up and stay shot up as I leaned against the SmartBoard for spinal support.
I can’t keep my hand raised. Doing it at all peeves my pinched nerve. It’s the same reason I can’t use a stress ball (tl;dr: an administrator noticed my fidget and recommended one, I tried to use it, my back screeched. Next time, I’ll go for the cube).
Minutes into an attempted signal, I once barked a frustrated, “Do you guys know you’re physically hurting me right now? I have an injured shoulder and this awesome thing called carpal tunnel and this is literally putting me in pain.”
It shut them down for the day.
Not so the next time I signaled. But at least one of the Hermiones cried out, “Guys! Quiet down! I’m gonna get purple tunnel!”
Bless him, really.