By Jennifer Dobner

SALT LAKE CITY, Nov 14 (Reuters) - A Utah parent has sued her school district in federal court challenging the constitutionality of restrictions imposed on student access to a library book about a lesbian couple raising a family.

"In Our Mothers' House" by author Patricia Polacco was removed from Davis School District library shelves and placed behind the counter last spring after complaints from some parents that a lifestyle they viewed as aberrant was favorably depicted in the book.

Under a decision made by a district committee in April, the book remains in its school library collections, but students need permission from their parents to check it out.

School officials acknowledge no similar limits have been placed on other titles in the library inventories of the Davis district, which encompasses an area north of Salt Lake City.

Parent Tina Weber objected to the restrictions, and attorneys for the American Civil Liberties Union filed a lawsuit on her behalf in U.S. District Court in Salt Lake City on Tuesday, saying the policy amounts to "prior restraint" that violates her children's free-speech rights.

No hearings have been set in the case, for which the ACLU is seeking class-action status.

Utah is not the first place parents have raised concerns about Polacco's book, which was published in 2009. A 2011 report by the ACLU of Texas showed "In Our Mothers' House" was banned in several schools in that state.

The Utah lawsuit asserts that by restricting access to a book based on its depiction of a family with same-sex parents, "the district has placed a discriminatory burden on the students' ability to access fully protected speech."

"Even worse, restricting access to 'In Our Mothers' House' and segregating it from the rest of the library collection places an unconstitutional stigma on the book and the students who wish to read it," the lawsuit says.

Weber has two children who attend Windridge Elementary School, where other parents first complained about the book, and she gave her youngsters permission to check it out.

Their ages are not specified in the lawsuit, but the legal director for the ACLU's Utah chapter said Weber read the story together with her 6-year-old daughter.

District officials have not yet been served with the lawsuit and cannot comment on its contents, spokesman Chris Williams told Reuters on Wednesday.

NOT ON THE SHELVES, 'BUT ACCESSIBLE'

"We still feel very comfortable with the process we followed, which is laid out in district policy," Williams said. "We still believe that at no time did we take parents out of the driver's seat. Parents still have the opportunity, if they want their child to read the book, to get it. It's not on the shelves, but it's accessible."

Parents were informed by letter of the restricted access after a district panel voted 6-1 in favor of requiring permission slips to check out the book. An elementary school committee of parents and educators decided earlier to allow only children in grades 3 and up to read the book.

"I was shocked when I heard that a handful of parents had made a decision about whether everyone else's kids could have access to this book," Weber said in a statement issued through Utah's ACLU office.

District officials have said that leaving the book on the library shelves would run afoul of Utah state sex education laws that prohibit any advocacy of homosexuality in the school curriculum. The district argues that curriculum extends to its library collections.

The ACLU lawsuit argues that library books are not curriculum materials and that including the book in library offerings does not amount to an endorsement of homosexuality.

The author of numerous award-winning children's books, Polacco has said she wrote the "In Our Mothers' House" after attending a school assembly where a child was silenced for speaking out about her same-sex parents.

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