Choose two age-appropriate books about one subject. One should be fiction and one should be nonfiction. For example, choose two books about the same subject, such as an animal. One should be a story, while the other should be an age-appropriate, nonfiction book detailing facts about the animal. After you read both stories to the class, explain how one story is made up while the other is based on facts. Ask the students about the differences between the two books and what makes one fiction and the other nonfiction. Choosing animal-based books for this activity makes explaining a little bit easier, as 5- and 6-year-olds know that animals don't wear clothes or talk, as they often do in fiction books for children.
Kindergarten students should be able to write short sentences. Have them write two stories composed of three to five sentences each. One story should be a made-up story about themselves. The other story should be about something that actually happened to them. Have them tell you which one is nonfiction, and ask them to explain the differences between the two.
Take your students to the school or local library and instruct them all to find a nonfiction book. Once they do so and are gathered back into a group, they should be able to get up in front of the class and explain what makes their book nonfiction. If they have picked out a fiction book instead, explain what doesn't make the book nonfiction. Encourage the students to check out their nonfiction book to take home and read.
The saying "never judge a book by its cover" doesn't apply when trying to separate fiction from nonfiction. Find several book covers and hold them up for your class. You can either use pictures of the book covers to make giant flash cards, or the actual books. Have your students try to guess which is fiction and nonfiction based on the book title and cover appearance. Ask questions, such as "Is there an actual picture on the cover or is it a cartoon drawing?" and "How does the title wording indicate whether something is fiction or nonfiction?"