School libraries in the United States of America have recently experienced an unprecedented number of external censorship attempts. Some censorship attempts, however, quietly occur when the school librarian engages in self-censorship, removing or refusing to purchase materials they consider to be controversial. This collection analysis study explored the extent of self-censorship in 90 Texas public high school libraries based on the exclusion of 55 controversial books in their collections, examining (1) possible relationships between a school’s characteristics and the absence of controversial books, (2) the extent to which the librarians are engaging in self-censorship, and (3) the controversial topics least likely to be included in collections. Findings suggest campus enrollment and district size were moderate to strong predictors of the number of expected books in a school library. More than half of the school libraries had the number of books one would expect based on their district size and campus enrollment. Books with transgender or LGBTQIA+ content were less likely to be found in school libraries, whereas titles featuring profanity, drinking, and drug use were most likely to appear, regardless of campus, district, and city size.