If you went to school in the U.S. in the past three decades, you were probably exposed to BOOK IT!, the reading reward program by Pizza Hut that has kids devouring books by the dozen in order to earn free pizza and other rewards. According to Pizza Hut, as of 2017, more than 14 million students across 620,000 classrooms have participated in BOOK IT! Here's what you need to know about the delicious—and educational—program.

1. BOOK IT! was inspired by the son of Pizza Hut’s then-president.

Pizza Hut's BOOK IT! program was created in Pizza Hut's Wichita, Kansas, offices in 1984. According to a video made by Pizza Hut, the program was created after President Ronald Reagan put out a call to America's businesses, encouraging them to get involved in education. Arthur Gunther, then-president of Pizza Hut, thought of his son, Michael, who had had trouble with reading due to eye problems when he was growing up. Gunther—who later told the Los Angeles Times that he was "truly motivated by my son and my love for him"—met with educators in the Kansas area with the goal of coming up with a program that would encourage kids to read and help them develop reading skills; what was developed became Pizza Hut's BOOK IT! program.

The idea behind BOOK IT! was simple: Reward students with certificates, stickers, buttons, and a single-topping Personal Pan Pizza for reading books. It was tested in Kansas schools before it—and its signature blue button—was rolled out nationwide in 1985.

Just over a month later, more than 7 million grade school students had participated across 233,080 classrooms. Gunther reported that three-quarters of students in the program exceeded their regular reading level. It also cost the chain an estimated $50 million in free pizza, plus $2.7 million in printed materials.

2. The creators of BOOK IT! got a letter from President Ronald Reagan.

On June 2, 1987, Reagan sent a message to BOOK IT! organizers, reading, in part:

"During this 'Year of the Reader,' we can all reflect that reading is essential to the vitality of the mind and to the success and accomplishment of almost every endeavor. As the Book-It Program prepares for yet another tremendous year of bringing the gift of reading to youngsters, I want to commend all those associated with the program for the outstanding work you do. Your efforts give help and inspiration to many and strengthen our Nation. I salute you."

3. BOOK IT! popped up on TV.

In a 1988 episode of Small Wonder, Vicki's class participated in BOOK IT! In the episode, two students have to finish their reading assignments. This being late-'80s primetime TV, one of the students creates a hip-hop book report comparing Robin Hood to Mr. T. They earned that pizza.

4. Bill Clinton declared an official "BOOK IT! Day" in Arkansas.

October 3, 1988 was a very special day. Arkansas Governor Bill Clinton issued an official proclamation declaring it "BOOK IT! Day," stating that the program was "an effective tool in motivating elementary students to read." He further noted that across Arkansas that year, 5711 classrooms with 142,775 students participated in the program.

5. Pizza Hut co-founded National Young Readers Week …

Pizza Hut extended BOOK IT! in 1989 with a week-long reading event that brought "celebrity" role models into schools to demonstrate the importance of reading to kids. ("Celebrities" are often local figures like school principals, though can include pop stars—see item 11 below!) Dubbed National Young Readers Week, the event was created alongside the Library of Congress Center for the Book. Pizza Hut proceeded to issue a challenge to school principals "to become shining examples for literacy by choosing one day to read their heart out all day long, from first bell to the last during National Young Readers Week." The event runs during the second week of November each year.

6. ... And the "Batman Principal" won the challenge in 2016.

Principal John Rizzo of Jonestown Elementary in Jonestown, Pennsylvania, won the National Young Readers Week principal challenge in 2016. He dressed up as Batman and visited classrooms in his school, promoting reading. Rizzo then went on the roof of the school to read to students. "We try to develop lifelong learners, especially lifelong learners of books and reading," the Bat-Principal told ABC27 News.

7. BOOK IT! is for homeschoolers, too.

While many students are exposed to BOOK IT! in public schools, it's available to homeschoolers too. (Online and virtual schools are also permitted.) The program runs from October 1 through March 31 each year, and students ages 5 to 12 (grades K to 6) are eligible to participate. There are two options: paper or digital. BOOK IT! prohibits clubs and other such non-school groups from participating.

8. Lots of people sell their old BOOK IT! buttons on eBay.

Vintage BOOK IT! promo items appear to be slightly collectible, especially the logo button which debuted in 1985. eBay has dozens of pins dating from the '80s and '90s—you can even see how the logo design changed over the years.

9. BOOK IT! was examined in a research study.

In 1999, a paper studying BOOK IT! was published. Entitled "Effects of extrinsic reinforcement for reading during childhood on reported reading habits of college students" (Psychological Record, 1999, by Flora, S. R., & Flora, D. B. [PDF]), the paper examined how pizza functioned as an extrinsic reward for reading. In other words, although reading carries intrinsic rewards like enjoying the story, the addition of extrinsic motivators like pizza or money (not part of the BOOK IT! program) can affect students' reading behavior. The study sought to determine whether those extrinsic rewards negatively affected later reading behavior—the concern being that perhaps without pizza or cash, students might stop reading.

From the paper's abstract (emphasis added):

Neither being reinforced with money or pizzas increased or decreased the amount college students read nor influenced their intrinsic motivation for reading. Answers to direct questions about BOOK IT! and parental pay for reading suggest that when a child is extrinsically reinforced for reading the child will increase the amount read, enjoyment of reading may increase, and if they do not yet know how to read fluently, the programs may help the child to learn to read. These results provide no support for the myth that extrinsic rewards for reading undermine intrinsic interest in reading. Rather, extrinsic rewards for reading set the conditions where intrinsic motivation for reading may develop.

10. Justin Bieber read The Cat in the Hat for BOOK IT!

In 2011, BOOK IT!'s "America's Biggest Bedtime Story" program presented Justin Bieber reading The Cat in the Hat by Dr. Seuss. The program exists to encourage parents to read bedtime stories to their kids. Bieber read the story to benefit the Pencils of Promise charity. The next year, BOOK IT! recruited Tim Tebow to read Green Eggs and Ham. (Back in 2007, John Lithgow kicked off the trend, reading his own kids' book, The Remarkable Farkle McBride.)