St. Pius X Catholic High School went fully virtual this week due to a spike in cases of COVID-19 largely traced to a Halloween party hosted by a student’s family, according to the Archdiocese of Atlanta.

As of Monday, the DeKalb County school had almost 50 active positive cases, an increase of 19 since the previous Friday. The rapid uptick led Principal Edye Simpson to announce that classes would remain virtual with no extracurricular activities all week.

The school is conducting contact tracing this week to determine which students can return to school Monday, said Maureen Smith, an archdiocesan spokeswoman. As of last week, the vast majority of the 1,100 students enrolled at St. Pius had been attending the coeducational school in person.

“We’re going to assume that the bulk of those cases came from this gathering,” Smith said. “It just became apparent that the safest thing we could do is send everybody home."

The family of a sophomore hosted the Halloween party, said Steve Spellman, president of the school, in a letter last week to families. Almost 80 students were present, and the school was learning of more partygoers every day, Spellman said. There were other large parties involving juniors and seniors, he said, but most of the cases reported over the past week have been sophomores.

“I am disappointed that despite the extraordinary effort and exorbitant expense to the school to ensure a safe environment, we have instances where safety protocols are totally ignored off school grounds,” Spellman said in his Nov. 4 letter. “Please know that this is not a political or ideological undercurrent or a subject of debate, but one of pure caution to protect our 1,100 students and 150 faculty and staff."

Two days later, Spellman ordered the entire sophomore class to quarantine until Nov. 15, two weeks after the Halloween party. He encouraged their siblings to quarantine as well.

“The brief enjoyment of some has created hardship for all,” Spellman said in that letter.

Spellman said Sunday the school would be closed Monday and Tuesday at the direction of the Health Department and the Archdiocesan COVID Task Force. Simpson announced Monday the closure had been extended through the week.

As contact tracing continues, the school will contact any families who need to remain quarantined after this week, Smith said.

“We hope that people will stay home and stay safe,” she said.