A California school district has settled out of court with parents who sued over its January 1 decision to incorporate the religious-based theory of "intelligent design" into philosophy lessons.
El Tejon unified school district officials have pledged never again to offer a course that "promotes or endorses creationism, creation science or intelligent design".
The district reopened the battle over teaching an alternative to evolution after December's case in which intelligent design was ruled out of bounds in science.
Ayesha Khan, legal director for Americans United for Separation of Church and State, which led both legal challenges on behalf of parents, said:
"This sends a strong signal to school districts that they cannot promote creationism or intelligent design as an alternative to evolution, whether in a science or a humanities class."
In the December case against Dover school district, Pennsylvania, a federal judge said that intelligent design was biblical creationism dressed-up and teaching it violated America's ban on religious proselytism in schools.
As a result, the school district stopped insisting science teachers tell students that evolution contained had inexplicable "gaps" and direct them to intelligent design as an alternative.
Intelligent design maintains that the intricacy of life can only be explained in terms of a higher mind. It declines to say whether this belongs to God, but it has been promoted by conservative Christians who view evolution as a secular affront to their belief in life's divine origins.
Judge John Jones' verdict was the first time a US-government-appointed official had ruled on intelligent design's legality in science lessons.
Although the judgment is only legally binding in Dover, the case was seen as a litmus test for the issue across the US, where the teaching of evolution is being challenged in a number of states.
The fact that Judge Jones is a church-going, registered Republican, appointed by President Bush himself, gave it added weight.
The Discovery Institute, the pressure group leading the challenge to evolution in US schools, said the judgement would only fan interest in intelligent design.
"Americans don't like to be told there is some idea that they aren't permitted to learn about," it said.
But the tide appears to be turning against critics of evolution.
All but one of the school board officials behind the Dover policy, introduced in 2004, lost office in the November elections, ousted by candidates vowing to overturn it.
Meanwhile, in Kansas, a decision to impose a science curriculum that requires teaching about the supposed flaws in evolution has galvanised Democrats and moderate Republicans to challenge conservative Christians who control the state's education board.
One Democrat candidate, Don Weiss, pledged to raise an unprecedented $100,000 (pound;56,518) to bankroll mailshots and possible television and radio advertisements. The conservative Republican incumbent he is bidding to unseat spent just $1,400 (pound;791) to win office four years ago, he says.
But Barbara Forrest, philosophy professor at Southeastern Louisiana university, said the political clout of the intelligent design movement could never be discounted. "It's part of the religious right and the religious right is not going away."