The organization sent a letter Tuesday requesting a meeting with superintendent Bryan Bowles about the picture book "In Our Mothers' House," which tells the story of three adopted children growing up with two mothers.
The district requires parents to sign a permission slip before students can check out the book. District officials have cited a state law that prohibits curriculum that advocates homosexuality.
Utah ACLU legal director John Mejia says federal courts consistently support student access to library books even if administrators disagree with the viewpoints within them.
Spokeswoman Shauna Lund says the district didn't have immediate comment early Wednesday.
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