Oh you bet it happens at school, I'm at that magical age when to most people, nothing is too immature, whether it be telling someone 'tell your mum I'll be late tonight', drawing stuff in other peoples books, passing the German in the corridor and mumbling something about 'ze var', getting 2 people on the teachers wheeled chairs and pushing them down the corridor at high speeds into each other, moving the teachers books from one side of their desk to the other just to annoy them and much more, I could write a book about all the stuff that happens. Don't worry, it all happens and all of it results in half the class hooting in laughter at the expense of someone else. I personaly think it's almost part of growing up, ammusing yourself but doing something so immature yet so funny.
I mean, just the other day, the teacher turned around to write something on the board so I stood up on my chair, took a nice big swing with an imaginary golf club, shouted 'FOUR' and quickly sat down before he could see who it was. Why did I do it ? because I was bored and thought it was funny and it's the same reason why people draw stuff on desks and books. Adults who've gone past that stage of immaturity don't understand, but to be honest, I doubt even those who do it know why.
Penis's complete with balls and sometimes hairs will magically appear on class room boards, text books, diary's (the books we keep notes for what our homework is etc) and desks. It's just to do with being immature and out of boredom. Sometimes it's done just to annoy someone else, nothing quite like seeing someones reaction opening their text book and seeing a penis drawn on every page. Not that I do it, but really, people just do it to amuse themselves
Always stand up for what is right, even if it means standing alone..