“How are you today?”
“Gentlemen.” (Followed by a fake hat tip and/or nod)
It doesn’t take much, does it? And make a point of it to the group that’s usually the loudest elsewhere, or the student that’s got a history of disrespect in someone’s class, and especially make a point of it to the kids that are waiting outside someone’s class because they’ve been sent out by their teacher. Why? Because it’s easy being polite to your well-behaved students that already have the etiquette down and this behaviour is the norm in their everyday routines, but this stuff isn’t natural to others and YOU might be responsible for creating the only environment in which they are talked to in a respectful way, as a mature developing adult, on equal par to you in terms of dignity. And even do it with the kid that got a detention from you in lesson, but you’ve just seen them in the corridors. It’s a different place and a different context.
Basically, be polite and respectful every chance you get, with everyone you meet. Respect is the oil that will keep the cogs running smoothly. The culture you build up through your little, informal interactions matters. The more people that do it, the more established will be the culture and the more everyone in your student and staff body will be surrounded by it. Then it can’t help but rub off on people. Someone clean spending time in a blacksmith’s shop will come out smelling like his environment and will be covered by it. Someone in rags and dirt spending time in a perfume shop will also come out with something of his environment. Coat everyone you meet in the perfume of good manners.