The list of challenged, censored, and banned children's books numbers in the thousands. Anyone can challenge a book; this occurs most frequently in public schools, when a parent, church, or advocacy group objects to a book in the curriculum. A challenge is an attempt to have the book removed or restricted, and is not always successful. A ban occurs when the book is removed from the school or library in question, usually on the directive of an administrator or governing board. Banned books lists reflect the trends of their time. For example, during the "satanism scare" of the 1980s and 90s, books that suggested witchcraft or occult practices, like Alvin Schwartz's Scary Stories series, were most likely to be challenged and banned. Staples of the children’s canon, like The Adventures of Huckleberry Finn, Bridge to Terabithia, and The Giver are also frequently challenged because they tend to appear in curricula most often.
In the first decade of the twenty-first century, the Harry Potter series topped the list of banned children's books. Philip Pullman’s His Dark Materials series made the top ten list during that period as well, reflecting the resurgence in “traditional family values” advocacy. Detractors claimed that the magical themes of these books suggested the occult, paganism, Satanism, or otherwise undermined religious beliefs. Books touching on the topic of homosexuality are always challenged. And Tango Makes Three, a picture book about a pair of male penguins that adopt a baby, has ranked high on the banned and challenged list since it was published in 2005. Books like Daddy’s New Roommate and Heather Has Two Mommies were frequently challenged in the 1990s, but fell off the lists in recent years due to a decline in popularity.
The American Library Association tracks and reports banned and challenged books, including type of initiators and reasons for opposition. Parents are by far the most common challenge initiators, trailed by school administrators, whose challenges usually represent a preemptive strike. Of institutions challenging and banning books, schools and school libraries rank the highest, followed by public libraries.
Challenges and bans are usually issued in the belief that this protects children from exposure to controversial topics. The most common reasons cited for a challenge or ban are “sexually explicit content” and “offensive language.” Violence, homosexuality, and racism also rank among the most frequently given rationale for censorship. Challenges due to homosexuality were considerably higher in the 90s than the 2000s, but the 2000s saw a marked spike in challenges on the grounds of sexually explicit content. Rarely, books are challenged due to inaccuracy or technical errors.
Anti-censorship advocates argue that children should not be sheltered from difficult topics or controversial viewpoints, and that parents or groups who challenge a book should not have the right to decide what is or is not appropriate for all children. The American Library Association opposes censorship, and their “Library Bill of Rights” states that “parents – and only parents – should have the right and responsibility to restrict the access of their children – and only their children – to library resources.”