A Virginia county closed all of its schools Friday because of intense backlash over a class assignment about Islam, with some parents alleging that their children were being subjected to Muslim indoctrination and educators emphasizing the importance of exposing U.S. students to the world’s fastest-growing religion.

A high school geography teacher in rural Augusta County asked students to try their hand at writing the shahada, an Islamic declaration of faith, in Arabic calligraphy. The task, community reaction to it, and a sudden influx of outrage from around the country — including angry emails, phone calls and threats to put the teacher’s head on a stake — led the school district to close rather than risk disruption or violence.

The county, in the Shenandoah valley west of Charlottesville, is the latest to wrestle with how Islam should be portrayed in the classroom and how students should learn about it. It’s a subject that has become increasingly fraught as concerns about Islamophobia have grown alongside fears of extremist violence and terrorism.

During the same week that Los Angeles and New York school systems debated whether to close due to emailed threats of attack, the Augusta County School District closed despite having no specific threat of harm to students. In a statement posted on the district’s website, officials said they were concerned about the “tone and content” of the messages they had received.

“We regret having to take this action, but we are doing so based on the recommendations of law enforcement and the Augusta County School Board out of an abundance of caution,” the statement said.

Augusta County Sheriff Randy Fisher said the superintendent and the school board decided to close the 10,000-student school system after district officials and the Riverheads High School teacher who gave the assignment received emails that seemed to increase in volume and vitriol as the week wore on. Most emails and messages assailed the school and the teacher for “indoctrinating” students in  Islam, and some referenced violence generally.

Fisher said he saw messages that called for firing the teacher and putting “her head on a stake.” Photos of beheaded bodies also were sent to the Riverheads principal. In a news release, the superintendent also said people indicated that they were planning protests at school buildings and that “some communications posed a risk of harm to school officials.”

The controversy started when teacher Cheryl LaPorte gave students a work sheet that instructed them to try their hand at writing the shahada. Reached Friday, LaPorte declined to comment.

Kimberly Herndon, whose son is in the class, posted a photo of the work sheet to her Facebook page this week. Under the heading “practicing calligraphy,” the work sheet says: “Here is the shahada, the Islamic statement of faith, written in Arabic. In the space below, try copying it by hand. This should give you an idea of the artistic complexity of calligraphy.”

The shahada translates to: “There is no god but God. Muhammad is the messenger of Allah.” Some translations start with: “There is no god but Allah.”

The students were never asked to translate the phrase, nor were they instructed to recite it or “adopt or pronounce it as a personal belief,” Schools Superintendent Eric Bond wrote in a news release. He noted that students are slated to do similar calligraphy exercises in units about China.

The superintendent said that students tried on head scarves in another lesson that taught them about the modest dress many Muslims adopt. Students will continue learning about world religions as required by Virginia’s statewide academic standards, school officials said. But in the future, students will practice calligraphy using a different sample that has nothing to do with the Islamic faith.

Bond and members of the school board did not respond to The Washington Post’s requests for comment Friday about the decision to close and the propriety of the assignment.

Some parents, including Herndon, were outraged at what they saw as an attempt to proselytize for Islam in a public school, a concern that has been echoed by parents in districts across the country regarding lessons that center on Islam. In Tennessee, there has been an uproar over teaching middle schoolers about Islam and ancient Islamic civilizations, prompting state lawmakers to consider legislation limiting the teaching of world religions to high schoolers, according to the Tennessean. At a middle school in Georgia, some parents were upset that their children were learning the five pillars of Islam, which are the central tenets of the faith, the Atlanta Journal-Constitution reported.

In Fairfax County, Va., one of the nation’s largest school districts, Rachel Butterfield said she took her concerns to administrators after her son — then in the fifth grade at Ravensworth Elementary — brought home what she found to be inappropriate lessons on Islam last year. It instructed students to read the Muslim statement of faith aloud, among other things. She said an assistant superintendent agreed with her concerns and decided to pull the lesson from the curriculum.

Butterfield said she loves Ravensworth and the teachers there, and doesn’t believe anyone was trying to spread propaganda.

“There was nothing malicious,” she said. “It was just this particular lesson. … It literally sent chills up my spine. I thought, ‘This can’t be right.’ ”

Fairfax County schools officials did not respond to a request for comment Friday.

Ibrahim Hooper, spokesman for the Council on American-Islamic Relations, said the controversy in Augusta County is “symptomatic of the hysterical anti-Muslim bigotry that we’re seeing in America at this current time.

“Anything to do with Islam or Muslims somehow becomes controversial, and you get this knee-jerk reaction based on misinformation, stereotypes, bias, and it’s really reaching frightening proportions,” Hooper said, adding that the lesson in Augusta was appropriate. “The shahada, the declaration of faith, is the foundation of Islam. You can’t learn about Islam without learning about the shahada.”

Experts say that teaching about religion is critical in public schools because religion — including Islam — is essential to understanding everything from ancient history to current events. Religious literacy has taken on an especially important role now, as religion has become a regular aspect of political rhetoric in part because of fears of terrorism linked to jihad. That makes it even more important for schools to teach about it, experts say.

“To be an educated person, to be a citizen, to be part of the global conversation, to be engaged in our world, religious literacy is essential,” said Charles C. Haynes, vice president of the Newseum Institute and founding director of the Religious Freedom Center. “More important than that is how are we going to live with one another in one of the most religiously diverse societies in the world without understanding one another?”

As Islamophobia has risen along with terrorism concerns — and just two weeks after the massacre in San Bernardino, Calif., which has been linked to extremism — learning about the religion can only help students understand what Islam is really about and what its true role is in the world, experts say.

“I think it’s clear from history that fear and ignorance create intolerance and hate,” Haynes said.

Haynes led the effort to formulate federal guidelines on how to teach about religion in public schools in 2000. He said teachers have to strike a balance between teaching about religious practices without having students mimic them.

“As far as the calligraphy, I don’t think it was a good choice to have students write out the shahada,” Haynes said, referring to the Augusta County lesson. “That’s really not appropriate. That’s like having students learn about Christianity by learning the Lord’s Prayer.”

Michelle Boorstein contributed to this report.