when I was a kid; one pulled on me that caused me a slight injury and one I pulled on Dad that caused him a slight injury.
That being said...bff's elementary school class once pranked their teacher pretty good. She went to a small Catholic school and in her small classroom was a "coat room" that took up the entire back wall of the classroom. It's a little hard to explain...I actually remember our school having the same thing. The doors were accordion style, folding open and shut and stayed shut during class time. Somehow bff convinced the whole class to join her in a prank...one day, everybody moved their desks backwards, inch by inch, when the nun had her back turned. Eventually, the nun left the room for some reason and the entire back room scooted their desks into the coat room and shut the doors. When the nun reentered the room, she was missing a bunch of students...
I also recently saw this prank on You Tube; it's from quite a few years ago but it was new to me, and it made me laugh...