A sticker in suburban Atlanta science textbooks that says evolution is "a theory, not a fact" is being challenged in court as an unlawful promotion of religion.

The lawsuit, filed by six parents and the Georgia chapter of the American Civil Liberties Union (search), begins Monday and is expected to last four days.

Cobb County (search) school officials adopted the disclaimer after science textbooks it adopted in 2002 were criticized by some parents for presenting evolution as fact. More than 2,000 people signed a petition opposing the biology texts because they did not discuss alternative theories, including creationism (search).

County school officials said their stickers simply encourage students to keep an open mind, but the lawsuit claims the warning promotes the teaching of creationism and discriminates against particular religions.

The U.S. Supreme Court ruled in 1987 that creationism was a religious belief that could not be taught in public schools along with evolution.

The stickers read: "This textbook contains material on evolution. Evolution is a theory, not a fact, regarding the origin of living things. This material should be approached with an open mind, studied carefully and critically considered."

"I'm a strong advocate for the separation of church and state," said one of the parents, Jeffrey Selman. "I have no problem with anybody's religious beliefs. I just want an adequate educational system."

A lawyer for Cobb County schools, Linwood Gunn, said he expects the disclaimer will hold up in court. He said the stickers "improve the curriculum while also promoting an attitude of tolerance for those that have different religious beliefs."