Geography lessons from year 9-11 were the best for me. Our teacher, Mr. Evans, was one of those stereotypical hopeless 50-yo types. No authority, a bit of a joke amongst the students (we'd call him Barry Evans).
Anyway - me and 3 of my friends sat together in the back right corner, next to the window. When Barry (lmao) went into the store-cupboard, I got up and pinched the Smart Board remote control. He was mid-presentation and I kept swapping slides - he didn't know what was going on.
So I passed on the remote across the classroom. Whilst he spent time trying to find it, one of my friends kept shouting at imaginary people outside the window. The rest of us got involved and started throwing our pencils and workbooks out the window, telling "them" to 'GO AWAY'.
Then I threw my shoe out of the window. I asked to go to the toilet and gathered all the stuff up from outside the building. I then started screaming "OWW. THAT REALLY HURT." back up at the window and I forgot there was a biology lesson underneath. The teacher in there opened the window and shouted at me
ANYWAY, I got back to the classroom and the teacher left us for a while, to get some classwork. We turned ALL of the desks the wrong way round and hid someone in the store cupboard.
We'd always shout, every lesson, "EASY!" (I think this was from Soccer AM?) and then "YOU SHAT AAAAAAAAAAAAAP". I remember the last lesson of the year - half of the school got involved. We saw people across the school yard in the language and art blocks shouting as well.
Aaaaaah, good times.