WATCH: Gay Character in Captain Underpants Sparks School Ban

Administrators at Arborwood Elementary School in Monroe, Mich., have decided to ban a popular children's book from the school's annual book fair because one of its main characters is gay.

The latest installment of author Dav Pilkey's popular, long-running children's series Captain Underpants -- titled Captain Underpants and the Sensational Sag of Sir Stinks A-Lot -- is being banned from sale at the book fair because it was deemed to be "controversial," according to Detroit TV station WXYZ.

"Scholastic notified us and the school that there was a book that may be a little controversial," Monroe Public Schools superintendent Barry Martin told WXYZ. Scholastic is the publisher of Captain Underpants and the sponsor of Arborwood Elementary's book fair. "The school decided we'll make it available online, but we won't make it available in the actual book fair itself."

The station reports that the decision to ban the book was made by the school's parent-teacher organization, out of concern that students make most of their book fair purchases without the supervision of parents.

"Most of the kids come in and they buy books and the parents aren't part of the selection," said Martin. "In this case, we felt it was necessary that if this book was going to be purchased, the parent needed to be involved in that."

Books in the Captain Underpants series were the most banned books of 2013 and 2014, according to the American Library Association.

Watch WXYZ's full report in the video below.