Teaching "intelligent design" to high school biology students violates laws prohibiting the endorsement of religion in public schools, a federal judge ruled Tuesday. The ruling in Pennsylvania is a major defeat for proponents of the controversial alternative theory about the origins of life.

"The evidence at trial demonstrates that ID [intelligent design] is nothing less than the progeny of creationism," wrote U.S. District Judge John E. Jones III.

He said the Dover Area School District's mandatory policy of reading a statement on intelligent design before teaching the theory of evolution to ninth-grade biology students violated the establishment clause of the First Amendment.

"I'm very proud of the plaintiffs for standing up and doing what they did," said newly elected school board member Lawrence Gurreri of the parents who sued the school. "Now we can get this school back to where it's supposed to be."

"I think it's a very sad day," said David Napierskie, a former school board member who supports ID.

Click here to read the judge's ruling.

Adherents of intelligent design are vastly outnumbered within the scientific community, although support for the theory is growing, particularly among evangelical Christians. The theory presupposes an "intelligent creator" and seeks to explain the supposed randomness of Charles Darwin's theory of evolution.

The Dover Area School Board enacted the policy of exposing students to ID in October 2004, and is believed to have been the first in the nation to do so. While the board argued that the intelligent designer needn't be God — some have said it could be a space alien — Judge Jones said such arguments barely disguised the board's true motives.

"No serious alternative to God as the designer has been proposed by members of [ID], including defendants' expert witnesses," Jones wrote. He later noted, "Not one defense expert was able to explain how the supernatural action suggested by ID could be anything other than an inherently religious proposition."

Defenders of the policy argued the school board was merely supplementing the teaching of evolution with an alternative theory that might better explain the origins of life.

"Because Darwin's theory is a theory, it continues to be tested as new evidence is discovered," read the Dover policy statement. "The theory is not a fact. Gaps in the theory exist for which there is no evidence. A theory is defined as a well-tested explanation that unifies a broad range of observations."

But, as Jones explained in detail, even ID proponents acknowledge that the "designer" in question is a supernatural force. The U.S. Supreme Court has repeatedly held that public schools may not endorse religion of any kind.

What made ID particularly suspect, Jones wrote, was the origin of the theory itself. ID came about after 1987, when the Supreme Court ruled that public schools may not teach "creation science," or creationism. Intelligent design, Jones said, was a cynical attempt by religious groups to sneak theology into the public schools.

"Those who disagree with our holding will likely mark it as the product of an activist judge. If so, they will have erred as this is manifestly not an activist court," Jones wrote.

"Rather, this case came to us as the result of the activism of an ill-informed faction on a school board, aided by a national public interest law firm eager to find a constitutional test case on ID, who in combination drove the Board to adopt an imprudent and ultimately unconstitutional policy."

He continued: "The breathtaking inanity of the board’s decision is evident when considered against the factual backdrop which has now been fully revealed through this trial. The students, parents, and teachers of the Dover Area School District deserved better than to be dragged into this legal maelstrom, with its resulting utter waste of monetary and personal resources."

School boards across the country had awaited Tuesday's decision with keen interest. Many may now be reluctant to test the waters themselves by introducing ID into biology classes.

Prior to Tuesday's ruling, the issue had stoked emotions within the divided Dover community, and eight school board members were turned out in a Nov. 8 election. They were replaced by opponents of the policy, who said they would not appeal the decision.

Bernadette Reinking, the board's new president, said intelligent design would probably be discussed in an elective social studies class after consultation with an attorney.

Gurreri, also one of the new board members elected in November, told FOXNews.com that all the media attention on the community of 20,000 was embarrassing and that tensions linger among residents. The parent of a Dover graduate and self-described churchgoer, he added that he was "very hopeful" residents would move past the ID battle and that the community's interest in the school system would remain as high as it's been in the past year.

Napierskie, the former school board member, said the judge overstepped his boundaries.

"[Jones] should have separated the issues and disagreed with the school board decision, but not rule on ID itself. Intelligent design still needs to be debated and discussed," Napierskie told FOX News.

Richard Thompson, president and chief counsel of the Thomas More Law Center in Ann Arbor, Mich., which represented the school district and describes its mission as defending the religious freedom of Christians, said: "What this really looks like is an ad hominem attack on scientists who happen to believe in God."

Even if the school board decides to appeal and the case reaches the Supreme Court, it is unclear whether the justices would decide to hear it, as the precedent on religion in schools has remained relatively fixed for the past half-century.

In the landmark Scopes Trial in 1925, a lower court ruled against a teacher who sought to teach evolution. But in 1968 the Supreme Court struck down an prohibition against teaching evolution in Arkansas. Twenty years later, a court decision effectively banned the teaching of creationism in all public schools.

Religious organizations have since tried several times to test the nationwide ban by arguing that there is no creationism in intelligent design. During the Dover trial, a school board member defended a statement he made in an interview, saying he "misspoke" when he advocated balancing evolution with creationism.

The defense also called several scientists as witnesses, rather than theologians. In a brief filed with the court, attorneys insisted that ID is a science, and "is not based on any religious authority or tenet of religious faith, nor does it seek to demonstrate the veracity of any religious authority or tenet of religious faith."

Other school boards across the country have also sought to diminish the prominence of evolutionary theory in their biology classrooms.

Earlier this month, a federal appeals court in Georgia heard arguments over evolution disclaimer stickers placed in a biology textbooks. A federal judge in January had ordered Cobb County school officials to immediately remove the stickers, which called evolution a theory, not a fact.

In November, state education officials in Kansas adopted new classroom science standards that call the theory of evolution into question.

Kansas Board of Education Chairman Steve Abrams, who supported that state's new standards, said the circumstances in Kansas and Pennsylvania are much different, given that the Dover board mandated intelligent design in its curriculum.

"We're not doing that," he said. "It's about teaching good critical thinking skills."

The Associated Press contributed to this report.