April Fools' Day is celebrated every year on April 1 by playing practical jokes and spreading hoaxes. The jokes and their victims are called April fools. An April Fool joke is revealed by shouting "April fool!" at the recipient, who becomes the "April fool".
These are a few April Fools' Day resources and teaching ideas you can use to bring this celebration into your class:
Enchanted Learning: http://www.enchantedlearning.com/crafts/aprilfool/
Seeker (origins of April Fools'Day): https://www.seeker.com/where-does-april-fools-day-originate-1769694656.html