When I was in school my friends and I used to be a bit destructive when it came to old computer parts during lunch times.
Any way during one lunch time we decided to relocate around the corner of the hall to get out of the sun. At this time one of my frineds found one of the school bell's within easy reach, having no pc parts to smash with us he decided to remove the bell cover off the school bell. After much efort on his part and much resistance from the bell he managed to remove the bell cover.
With a critical eye to my friends handy work we all examied the destruction of the bell, during that time i noticed some exposed wires tucked aside.
Without much thought or care on my part I decieded it would be a good idea to rewire the bell for kicks.
About 10min later with the help of a screwdriver that seemed to appear out of thin air, with lunch time growing to a close we decided it would be a good idea to hide our mischief so my friend who pulled the bell cover off, dosed the whole thing in coke and hooked the bell cover up so it hid my handy work .
As lunch came to an end we all waited for the bell to ring, when it did we were all kind of suprised with what happened the bells actualy rang---- for less than a second. All over the school the bells just rang for a few secinds then stoped mid ring.
With that done we all when to class, an hour later we all got ready for the bell to ring we waited, we waited and someone actualy stood up and said "should the bell have rung by now " the teacher looks at their watch and says "yep. ok off to your next class".
To make a long story short my friend and I sabotaged the school bell's for what seemed like most of that year but was probly only 3-6 months.
It caused much unhappiness with the teaching staff when you could worm your way out of class 15min early if they forgot their watch :)
My friends and I still have a laugh about it to this day .