A Plaquemines Parish high school’s decision to bar a Rastafarian student because his dreadlocks violate the school’s dress code has drawn a complaint from the New Orleans chapter of the American Civil Liberties Union, which says the policy violates the student’s right to practice his religion.

In a letter sent to school administrators Monday, ACLU staff attorney Candice Sirmon compared South Plaquemines High School’s requirement that the unnamed student cut his hair with a ban on religious icons. She said the policy amounts to discrimination against his religious beliefs, which require that he not cut his hair.

“We would object if the school were to tell a Christian student they could not wear a cross or if it were to permit the wearing of religious icons of one faith and prohibited those of another faith,” Sirmon said in the letter. “In discriminating against John Doe’s religious beliefs, the school is expressing a preference for certain religions, which is unacceptable.”

Perhaps most closely associated in the popular media with singer Bob Marley and other reggae artists, Rastafarianism is an Afro-Caribbean religion that blends Ethiopian and Jamaican cultural roots with aspects of Christianity and Judaism. Some adherents believe men are required to wear their hair long and in dreadlocks.

Besides violating the student’s religious rights, the ACLU said, the school’s decision infringes on his right to free expression because the hairstyle communicates that the student “is a Rastafari for whom traditional religious practices are important.”

The student was told on the first day of school that he would have to cut his hair, which reached just below the bottom of his shirt collar, and he was sent home on the second day when he had not done so, according to the letter. The school’s dress code prohibits male students from allowing their hair to grow beyond the top of their shirt collar or from putting it in a ponytail.

The ACLU would not reveal the identity of the student.

A School Board member told the student’s mother that he would be allowed to return to school if he pinned his hair up, but even after he did so, administrators continued to refuse to allow him into the school, according to the letter. He has already missed 10 days of classes on what the ACLU said is essentially an “indefinite suspension.”

Plaquemines Parish school officials did not respond to several requests for comment Monday.

In its letter, the ACLU cited both the U.S. Constitution’s guarantee of freedom of religion and a Louisiana law that prohibits any burden on religious liberty that does not fulfill a “compelling interest.” It also noted that in 2010, the U.S. 5th Circuit Court of Appeals ruled that a Native American student’s rights were violated when he was told he had to cut or hide his hair, which he had grown out because of his religious beliefs.

The ACLU has called for a hearing on the issue and demanded that the student be allowed back in school, allowed to make up the work he has missed and not be penalized for his absences.

Follow Jeff Adelson on Twitter, @jadelson.