What percent of schools list The Hitchhikers Guide to the Galaxy?

There is no definitive answer to this question, as the data on what books are listed in school libraries is not centrally collected or publicly available. However, a 2007 study by the American Library Association (ALA) found that The Hitchhiker's Guide to the Galaxy was one of the 100 most challenged books in American libraries between 1990 and 2006. This suggests that the book may be less likely to be listed in school libraries than books that are not considered controversial.