Two weeks into the new term, COVID-19 has temporarily closed the first Philadelphia School District building.

Emlen Elementary in East Mount Airy will be shut for in-person learning until Sept. 24, officials said in a letter to families. The K-5 school enrolls about 300 students, all of whom are too young to be vaccinated.

“Due to multiple positive cases of COVID-19 in our school, the Philadelphia Department of Public Health (PDPH) has determined that our school building will temporarily close from 9-13-21 to 9-23-21 to help stem the spread of the virus,” principal Tammy Thomas wrote to Emlen families Monday. “Students and staff may not return to our school building during this time.”

Learning will continue during the building closure; teachers will be instructing students remotely, as they did for most students for the entirety of the 2020-21 school year.

Students who did not share a classroom with an employee or student who tested positive for COVID-19 do not need to quarantine, the letter said.

Schools officials are following Philadelphia Department of Public Health guidelines in deciding when to quarantine students, classes, or close entire schools.

Three or more cases in one classroom requires the class to quarantine; three or more cases across a grade requires a grade to quarantine; six or more cases across grades within a school within 14 days triggers temporary building closure.

» READ MORE: 20,000 Philly schools employees must get vaccinated by Sept. 30. Here’s what happens if they don’t.

COVID-19 cases among school-aged children are rising sharply.

Superintendent William R. Hite Jr. has stressed the importance of in-person learning, especially after 18 months of interrupted learning for most children. He has also said he fully expects temporary school closures in the 120,000-student, 215-school district because of outbreaks.

Officials have said they’re doing all they can to mitigate risk. All district students and staff must wear masks, except while eating. Staff must be vaccinated — though some exceptions are allowed, and those employees who choose not to get vaccinated will submit to COVID-19 testing twice a week. Officials encourage keeping three feet of space between students, but that’s often not possible in some Philadelphia classrooms.

» READ MORE: Philly’s bus driver shortage is a ‘crisis,’ leaving kids missing school or stranded

Staff are tested weekly, but the district has moved away from asymptomatic testing of students, which happened last spring when some students returned to classes two days a week. (Students who play some contact sports and those who participate in performance extracurriculars such as choir and band do receive COVID-19 testing.)

Several city councilmembers and the Philadelphia Federation of Teachers have called on the district to reinstate asymptomatic testing of students, in line with CDC guidance. Hite has said the asymptomatic testing disrupted learning.

The district maintains a public COVID-19 dashboard, but no student data are yet available.