Judge Clarence Cooper of U.S. District Court wrote that the stickers, perhaps inadvertently, ''convey a message of endorsement of religion,'' violating the First Amendment's separation of church and state and the Georgia Constitution's prohibition against using public money to aid religion.

''I'm ecstatic,'' said Jeffrey Selman, one of five parents who won the suit against the school district. ''Science is religion-free, and it has to stay that way.''

Selman said he thought the ruling would be a warning to fundamentalists nationwide, especially in Dover, Pa., where parents have sued their school board for telling teachers to read students a statement that suggests an alternative to evolution, intelligent design, which posits a creator.

A lawyer representing the Dover school board said that Cooper explicitly said that he was not ruling on whether public schools could teach intelligent design.

In his ruling, Cooper applied the Lemon test, which was laid out by the Supreme Court in a 1971 case, Lemon v. Kurtzman. Under that test, the sticker would violate the Constitution if it did not have a secular purpose, if its primary effect advanced or inhibited religion, or if it created an excessive entanglement of the government with religion.

Cooper upheld his earlier ruling that the sticker's purpose was secular enough, that it fostered critical thinking and presented evolution to students who oppose it in a ''not unnecessarily hostile'' way.

But he found that the effect of the sticker in singling out evolution, given the roots of the sticker and its language in religious challenges to evolution, was to convey a message of endorsement of religion. His 44-page order argued that any informed, reasonable person would know the religious controversy behind the sticker.

The Cobb County school system adopted the stickers in 2002 along with well-regarded textbooks that taught evolution. During the textbook adoption process the school board realized it would have to change its policy, which for years had forbidden any teaching about the origin of humans in elementary and middle schools and in required high school classes, ''in respect for the family teachings of a significant number of Cobb County citizens.''

The school board argued that the sticker was a neutral gesture to parents who had lost the fight against evolution. ''I was a little disappointed but not terribly surprised,'' said Linwood Gunn, a lawyer for the schools. ''I think the court adopted the viewpoint that any potential disparagement of evolution is equivalent to promotion of religion.''

The board said it would review the decision and decide whether to appeal.

Marjorie Rogers, a parent and creationist whose petition drive led to the sticker, said she was disappointed by the decision, but she ''never was thrilled'' with the sticker's wording, which she found weak.