Just had the best idea for a way to prank your school.
What you need : Slenderman drawings (like from the game)
A mannequin dress as Slenderman
What to do: Get to school early, before most people would be there. Place the pictures around the school in various locations. Leave them out for a day or two. Then, during the day, while most people would be in class, bring out the mannequin and place it in a secluded location
Have fun! And Happy Halloween