So this basically happens during the Marauders Era. It is when they are first years. 

Dumbledore: Order! Order! LISTEN TO ME OR I WILL FIRE YOU!

The teachers stopped chatting and turned to face Dumbledore. 

Dumbledore: Thank you. *begins to walk back and forth for drama* You may be wondering why I have brought you here today. *pauses for suspense* This is our first Teachers Lounge Meeting. *turns to face teachers* What is the Teachers Lounge you may ask? *McGonagall rolls eyes* It is a safe place for the teachers to raise any....concerns they may have about how I run this school. I will also be teaching mandatory classes twice a week for the teachers. 

McGonagall raises hand.

Dumbledore: Yes, Minerva?

McGonagall: What will these classes be? I mean, they must be very important if they are mandatory.

Dumbledore clasped his hands together and sits on desk.

Dumbledore: I am so glad you asked! The classes will be Getting Your Ships Together 101 and Student Relationships Assessments. 

Teachers start whispering, very confused looks on their faces. 

McGonagall: And why exactly are these "important" classes.

*Dumbledore shakes head* He walks over to McGonagall and sits next to her.

Dumbledore: Poor, poor Minerva. So ignorant. Isn't it obvious? I am starting a betting pool on the different student relationships at Hogwarts, but teachers will get mad at me if they lose money. So I am staring classes on how to give students a.....push in the right direction so that you can win money, as well as how to see the potential of different ships! How did you not understand that? *Minerva rolls eyes* Well, that's it for the first Teachers Lounge meeting! Classes are on Monday and Thursday at 9 o'clock sharp. Betting pool starts next week, all teachers required to join! 

Dumbledore gets up and skips out of the room, humming to himself. The teachers sigh and pack up, wondering what they have gotten themselves into.