A Virginia school district closed its schools on Friday amid an angry backlash, including a possible “risk of harm to school officials,” over an assignment that asked high school students to copy a Muslim creed in Arabic calligraphy.

Students in a world geography class at Riverheads High School in Staunton, Va., had been asked to try their hands at copying a passage known as the Shahada, or declaration of faith in Islam. The work sheet distributed to students on Dec. 11 said: “This should give you an idea of the artistic complexity of calligraphy.”

But some parents accused the teacher of trying to convert their children to Islam, inciting an angry outcry in the largely rural district nestled in the Shenandoah Valley. The Shahada is recited as part of daily prayer, and translates to, “There is no God but God, and Muhammad is the messenger of God.” Speaking the Shahada before witnesses is an important step in converting to Islam.

The complaints were further fueled by the teacher inviting female students to wear a head scarf, as many Muslim women do. The number of angry calls and emails to the district increased sharply as this week wore on, fueled by growing media coverage of the controversy.