ThunderRidge High School has become the fourth high school in the Douglas County School District to switch to virtual learning amid logistical pressures from COVID-19.

A letter sent to the Highlands Ranch school’s community on Oct. 2 said there have been at least seven positive cases confirmed at the school since Sept. 21. More than two dozen staff were in quarantine.

A spokeswoman said in total there are 385 people quarantined at the school, which enrolls 1,900 students.

The school decided to conduct virtual learning because so many teachers are quarantined and there are not enough substitute teachers available to manage in-person learning, according to the letter.

The school was scheduled to begin full virtual learning on Oct. 5. Students would follow their regular class and cohort schedule during virtual learning and athletic activities would continue as usual.

Students would return to in-person learning after Oct. 19 following fall break.

In September, Mountain Vista High School, Douglas County High School and Castle View High School switched to virtual learning for two weeks under similar circumstances.