“Our books are being shadow-banned,” said Nina Perez, a Jacksonville resident and a director for MomsRising, an advocacy organization opposing the restrictions. “They get mired in an administrative process.”

Tracy Pierce, a Duval school district spokeswoman, said in an email last month that the actions had followed guidance from the state’s Department of Education. At no time should classrooms have been without reading material, she said, since students still had access to approved books and collections. She acknowledged that “a small number of principals did close or overly restrict” media centers briefly and were advised to restore access.

Mr. DeSantis has reacted aggressively to criticism that public schools are banning books. He dismissed news reports that Duval County schools had removed a title about the baseball player Roberto Clemente as “a joke,” accusing critics of “manufacturing” a narrative about book bans.

The book, which addresses the racism that Mr. Clemente faced, was removed and then restored in February after a review. Last month, the state’s education commissioner named the title, “Roberto Clemente: Pride of the Pittsburgh Pirates” by Jonah Winter, a book of the month for third through fifth grades.

At a news conference last month, Mr. DeSantis stood behind a sign that read “Exposing the Book Ban HOAX” and said that the state was trying to protect children from pornographic material. The event began with a presentation on books reported to districts for removal — including “Gender Queer,” by Maia Kobabe and “Flamer,” by Mike Curato — and highlighted scenes about sexual contact and masturbation.

“This idea of a book ban in Florida, that somehow they don’t want books in the library — that’s a hoax,” Mr. DeSantis said. “And that’s really a nasty hoax, because it’s a hoax in service of trying to pollute and sexualize our children.”

Critics in the state are pushing back. In March, Democracy Forward, an advocacy organization, filed a lawsuit with the state on behalf of the Florida Education Association and other groups challenging the rules, arguing that they censor educators, limit students’ access to books and harm public education. The Florida Freedom to Read Project organized a rally in Tallahassee last month with authors and free speech activists to protest censorship.