When I was in elementary, middle and high school, circa 1967-1981, almost every teacher had a "fanny paddle" prominently displayed on their desk. Some used them physically, some used them psychologically. There wasn't a problem with 5th graders having sex in the classroom, nor were there any of the other discipline problems we are seeing in classrooms today. I can say now in hindsight that every time I was paddled I deserved it and I suffer no lasting harm from any paddling I ever received.
I suppose the "threat" of the fanny paddle was worse than the punishment.
In my Junior High school days, we had a male teacher whose favorite weapon was his extremely strong right hand. When he caught you goofing off, he quietly approached you, grabbed your bicep and, with a grip of iron, "lectured" you while squeezing your muscle with all his might.
After the first few days of school, there were no longer "class clowns" in his class.