In January, a federal judge ordered Cobb County, Georgia, school officials to immediately remove the stickers, saying they were an endorsement of religion. The ruling was appealed to the 11th U.S. Circuit Court of Appeals, which will hear arguments on Thursday.
Advocates on both sides say the appeals court's decision will go a long way toward shaping a debate between science and religion that has cropped up in various forms around the country.
"If it's unconstitutional to tell students to study evolution with an open mind, then what's not unconstitutional?" said John West, a senior fellow with the Discovery Institute, a Seattle-based think tank that supports intelligent design, the belief that the universe is so complex it must have been created by a higher power. "The judge is basically trying to make it unconstitutional for anyone to have a divergent view, and we think that has a chilling effect on free speech."
Opponents of the sticker campaign see it as a backdoor attempt to introduce the biblical story of creation into the public schools – something the U.S. Supreme Court disallowed in a 1987 case from Louisiana.
"The anti-evolution forces have been searching for a new strategy that would accomplish the same end," said Kenneth Miller, a professor of biology at Brown University and co-author of the science book that was stickered. "That purpose is, if not to get evolution out of the schools altogether, then at least undermine it as much as possible in the minds of students."
The disclaimers were placed in the books in 2002 by school officials in Cobb County, a suburb of about 650,000 people. The stickers were printed up after more than 2,000 parents complained that science texts presented evolution as a fact, with no mention of other theories.
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."
The school board called the stickers "a reasonable and evenhanded guide to science instruction" that encourages students to be critical thinkers.
Some parents, along with the American Civil Liberties Union, sued, claiming the stickers violated the constitutional separation of church and state.
U.S. District Judge Clarence Cooper ruled that the sticker "conveys an impermissible message of endorsement and tells some citizens that they are political outsiders while telling others they are political insiders."
In Pennsylvania, a federal judge has yet to decide whether the Dover Area School District can require ninth-grade biology students to learn about intelligent design. A few days after the trial ended earlier this fall, Dover voters ousted eight of the nine school board members who adopted the policy.
The same week, state education officials in Kansas adopted new classroom science standards that call the theory of evolution into question.
In 2004, Georgia's school superintendent proposed a statewide science curriculum that dropped the word "evolution" in favor of "changes over time." That plan was soon scrapped amid protests from teachers.