AUSTIN — Texas Attorney General Ken Paxton is defending a state law that requires schoolchildren to say the Pledge of Allegiance by joining a lawsuit that could determine the legality of similar mandates nationwide.

On Tuesday, Paxton intervened in a lawsuit that was filed against the Cypress Fairbanks school district last October. Kizzy Landry sued the district and several officials after a principal kicked her daughter, India, out of school for sitting during the Pledge.

Landry supported her child's decision to sit. And while Texas allows parents to sign a waiver letting their child opt out of saying the Pledge, Landry contends that the law requiring kids to say it in the first place violates their free speech rights. Paxton disagreed, arguing: "School children cannot unilaterally refuse to participate in the pledge."

"Requiring the pledge to be recited at the start of every school day has the laudable result of fostering respect for our flag and a patriotic love of our country," Paxton said in a prepared statement. "This case is about providing for the saying of the pledge of allegiance while respecting the parental right to direct the education of children."

The case is set for trial April 15. Experts said its outcome could have ripple effects nationwide.

"We've only ever seen one case litigated involving the mandate to say the Pledge in modern history," Frank LoMonte, one of the nation's foremost experts on free speech and student rights, said in an interview. "If this one were to go up [to the U.S. Supreme Court], it would be quite influential, not just in Texas but across the country as the first of its kind."

The case

India said that by age 17, she had refused to stand for the Pledge around 200 times. Then she switched schools to Windfern School of Choice in Houston, where the staff began to discipline her for sitting. When she refused to stand for the Pledge while in the principal's office, she was kicked out of school.

"This is not the NFL," a school secretary told India, according to the lawsuit. "Principal [Martha] Strother suggested that, instead of sitting, India could write about justice and African Americans being killed."

For four days, the Landrys were told that India, who is black, couldn't come back to school until she agreed to stand for the Pledge. They refused and instead went on television to criticize the school's statements. The next day, the principal reversed her decision and let India return.

But her mother said her daughter's grades suffered. India, now 18, did not graduate. It's unclear whether Kizzy Landry signed a waiver to let India opt out of the Pledge.

In July, a federal judge refused to throw out the case, saying that India could proceed with First Amendment free speech and 14th Amendment due process and equal protection claims against the district and its leaders.

The attorney general has the right to intervene in cases when the constitutionality of a state law is questioned. On Tuesday, Paxton filed a motion to do so.

The district, in responding to a request for comment, reiterated that state law requires students to stand for the Pledge unless their parents sign a waiver.

The Landrys' attorney, Randall Kallinen, criticized Paxton's statements as "very political." The American Civil Liberties Union of Texas agreed.

"Once again, it appears that Ken Paxton is using his authority to foster division within our state through political posturing," said Andre Segura, legal director for the ACLU of Texas. "Educators and lawmakers alike should take this as an opportunity to create a discourse on civic engagement, rather than to punish students."

The precedent

Paxton argues that the Supreme Court has upheld a parent or guardian's "fundamental interest in guiding the education and upbringing of their children. That interest rightfully includes determining whether their children should participate in the time-honored tradition of reciting the Pledge of Allegiance to the United States flag."

LoMonte, the free speech and student rights

expert, disagreed, citing other cases.

In 1943, the Supreme Court ruled that forcing schoolchildren to salute the flag violated their First Amendment right to free speech. Then, in 1969, the court ruled that school officials can suppress students' free speech rights only if they can prove the conduct would "materially and substantially interfere" with the school's operation.

States have tried to skirt these rulings by allowing parents to let their kids opt in or out of saying the Pledge. A Florida law similar to Texas' was upheld after its legality was challenged. But the Supreme Court didn't take up the case, meaning the precedent applies only in Alabama, Florida and Georgia.

LoMonte said punishing a child for refusing to stand flies in the face of the earlier Supreme Court decisions.

"A school cannot impose discipline on somebody who does nothing more than quietly sit down," he said. "The issue of the parental waiver certainly muddies the law, as there is definitely some strain of legal authority that says parents have a constitutional right to decide how their kids are raised."

LoMonte said the case could imperil compulsory Pledge laws across the country if it ends up in the Supreme Court, a process that could take years. With students like the survivors of the shooting in Parkland, Fla., becoming more politically active, LoMonte said the rights of students are ripe for discussion.

"It really would be interesting to see if this is really the opinion of judges today," he said. "It's kind of hard to tell members of the Parkland generation that they are pieces of property owned by their parents."