It is a foundational democratic tenet taught in every basic U.S. history course: the Constitution bars the government from endorsing an official religion or favoring one over others.

But moves by two Republican-governed states - Louisiana's requirement that public schools display the biblical Ten Commandments and Oklahoma's mandate that public schools teach the Bible - take aim at the Constitution's "establishment clause," long understood by courts as separating church and state.

Lawmakers in 29 states have proposed at least 91 bills promoting religion in public schools this year, according to Americans United for Separation of Church and State, an advocacy group backing a lawsuit challenging Louisiana's law. Rachel Laser, its chief executive, said the group tracked 49 similar bills in 2023.

The movement is fueled by opposition to what conservatives call liberal curriculums, including a focus on diversity and LGBT rights, and by the U.S. Supreme Court's willingness to overturn precedent as it moves American law rightward.

Republican Louisiana Attorney General Liz Murrill, whose office is defending the Ten Commandments law in court, said on Monday that legislators frustrated by a lack of discipline in schools turned to the biblical precepts to "start a conversation about order."

"That's the fundamental message that exists in our legal structures about what Moses stood for and what the Ten Commandments stood for," Murrill told a press conference.

When asked how non-religious parents could respond to the law, Republican Louisiana Governor Jeff Landry told the press conference they could tell their children not to look at Ten Commandments posters.

Conservatives are hopeful that legal challenges will give the Supreme Court an opportunity to reconsider longstanding limits on religious expression in public schools.

"They see the writing on the wall of what the Supreme Court is doing," said law professor Steven Green of Willamette University in Oregon, who wrote the book "Separating Church and State: A History."

A week after Louisiana in June became the first state to require schools to display the Ten Commandments since the Supreme Court struck down a similar Kentucky law in 1980, Oklahoma's schools superintendent, Ryan Walters, directed all public schools to teach from the Bible.

Under Oklahoma's guidelines, teachers will be given a copy of the Bible and focus on its historical context in Western society and American history, its literary significance, and its influence on the arts and music. Several Oklahoma school districts have refused to alter their curriculums to accommodate the policy change.

Walters did not respond to a request for comment.

In both states, officials said the religious texts are important to understanding the birth of American government. The claim echoes arguments by some Christian conservatives that the United States was founded as a Christian country, an idea many historians call inaccurate.

CHRISTIAN LAWMAKERS

The National Association of Christian Lawmakers (NACL), founded in 2020, has coordinated legislative efforts across different states. It has produced three dozen "model" bills for introduction in state legislatures, including one on the Ten Commandments and another requiring schools to display "In God We Trust" signs.

Republican Louisiana Representative Dodie Horton, the sponsor of that state's Ten Commandments bill and a member of the association, did not respond to a request for comment.

The next major battleground could be Republican-governed Texas, which passed the first law in the United States last year letting public schools hire chaplains as counselors. Similar bills subsequently were introduced in more than a dozen states.

The Texas board of education will decide in November whether to approve a new elementary school curriculum that includes Bible teachings. Texas Republican lawmakers are likely to revive bills requiring the display of the Ten Commandments in schools and allowing publicly funded vouchers to pay for student tuition at private religious schools.

In an interview last month at the Republican National Convention, the NACL's founder, former Arkansas state Senator Jason Rapert, argued that religious values are disappearing from American public life, imperiling the future.

"The Judeo-Christian history and heritage of the nation has been torn down in many places," Rapert said.

Opinion polls show that while a solid majority of Americans identify as Christians, the number has been declining for decades.

A CONSERVATIVE SUPREME COURT

The Supreme Court in 1962 ruled that school-sponsored prayer in public schools violated the establishment clause. But the court, which now has a 6-3 conservative majority, has taken an expansive view of religious rights in some important cases in recent years.

In 2022, it ruled that a Washington state public school district violated the constitutional rights of a Christian high school football coach who was suspended for refusing to stop leading prayers with players on the field after games. In doing so, it abandoned a 1971 precedent that had outlined how to determine if a law violated the Establishment Clause.

The ruling galvanized conservative Christians, as did the court's decision days earlier rolling back abortion rights.

The court also has made it easier for religious schools and churches to receive public money; exempted family-owned corporations from having to provide employee insurance coverage for women's birth control on religious grounds; and backed a Christian baker and a Christian web designer who refused to provide services for same-sex weddings.

Rapert called the court's evolving view on religion in public life a "great opportunity."

If new laws on religion and public schools are challenged at the Supreme Court, it will have to answer questions such as whether they make a denominational preference or coerce people to participate in a religion, said law and religion professor Michael Helfand of Pepperdine University in California.

"Should I feel religiously coerced if the state puts up the Ten Commandments in my classroom?" Helfand asked. "I could see a court going either way on that."