Allow me to post the full quote from PICO, and emphasize the passage you likely wished to avoid posting:
(c) Petitioners possess significant discretion to determine the content of their school libraries, but that discretion may not be exercised in a narrowly partisan or political manner. Whether petitioners' removal of books from the libraries denied respondents their First Amendment rights depends upon the motivation behind petitioners' actions. Local school boards may not remove books from school libraries simply because they dislike the ideas contained in those books and seek by their removal to "prescribe what shall be orthodox in politics, nationalism, religion, or other matters of opinion." West Virginia Board of Education v. Barnette, 319 U.S. 624, 642 . If such an intention was the decisive factor in petitioners' decision, then petitioners have exercised their discretion in violation of the Constitution. Pp. 869-872.
QED: Communities have discretion to determine what will and what will not be included in school libraries. The question is whether, say, omitting books on that promote trans ideology is narrowly focused or not. I don't see it as any less narrowly focused than, say, not including books on white nationalism. Both are extreme views that have opponents on the left and right.