This page explains how to solve the quest "School Pranks" in Yo-kai Watch.
Start the Quest
Talk to the janitor in the room east of the principal's office in Springdale Elementary to start the quest.
Find the out-of-place stuff!
The misplaced items are not marked on the map, so you will have to walk around the different rooms of the school until an exclamation mark appears over your head. Check that location to find a misplaced item.
All pranked items found!
After you have found all of the items, go back and talk to the janitor to complete the quest.
Return to the List of Quests.