A coalition of Texas families and religious leaders filed a federal lawsuit Saturday challenging a new state law that mandates the display of the Ten Commandments in every public school classroom.

The law, signed by Gov. Greg Abbott on June 21, requires all Texas public schools to post a state-approved version of the Ten Commandments in a prominent location in each classroom by Sept. 1. The poster must be at least 16-by-20 inches in size and printed in large, legible font.

The lawsuit, supported by the American Civil Liberties Union, Americans United for Separation of Church and State, and other religious freedom groups, argues that the mandate violates the First Amendment’s Establishment Clause by promoting a specific religious doctrine in public education.

Plaintiffs include a diverse group of parents and students who identify as Christian, Jewish, Muslim, Unitarian, atheist and members of the Nation of Islam. They say the law infringes on their constitutional rights and disrespects religious diversity in public schools.

“This law sends a clear message that students who don’t subscribe to a particular religious tradition are outsiders in their own classrooms,” said Rachel Laser, president of Americans United for Separation of Church and State. “The government should not be forcing religious texts into public school curricula.”

Supporters of the law, including Lt. Gov. Dan Patrick and Sen. Phil King, who authored the bill, say the measure restores recognition of the country’s Judeo-Christian heritage and offers moral guidance to students.

“The Ten Commandments are part of the foundation of American law and culture,” Patrick said. “This is about history and values, not religion.”

The law does not allocate state funding for the posters, but allows schools to accept private donations or use discretionary funds to comply.

The legal challenge is expected to ignite a national debate and could end up before the U.S. Supreme Court. The issue echoes a 1980 ruling in Stone v. Graham, in which the high court struck down a similar law in Kentucky, finding it unconstitutional to post the Ten Commandments in public school classrooms.

However, conservatives point to a more recent 2005 Supreme Court case, Van Orden v. Perry, which upheld the constitutionality of a Ten Commandments monument on the Texas Capitol grounds, as precedent in their favor.

Until the courts weigh in, school districts across Texas are preparing to comply with the new mandate while closely monitoring the lawsuit’s progress.

“This is a test of whether Texas public schools will remain a place for education, not religious indoctrination,” said David Donatti, a staff attorney with the ACLU of Texas. “We intend to fight this law every step of the way.”