The Los Angeles Unified School District will require all students and employees who are returning for in-person instruction to participate in weekly COVID-19 testing — regardless of vaccination status, the district announced Thursday.

“This is in accordance with the most recent guidance from the Los Angeles County Department of Public Health,” Interim Superintendent Megan K. Reilly said in a statement.

LAUSD, the nation’s second-largest school district, had previously said that fully vaccinated students and employees would not require testing. But as schools district-wide prepare to reopen for in-person instruction on Aug. 16, L.A. Unified said it’s closely monitoring evolving health conditions and adapting its response.

Students and employees can sign up for testing here. There are several, free L.A. Unified testing sites throughout the county, and mobile teams will also be present to provide testing before the first day of school.

In addition to regular testing, safety measures will include: masking for all students, staff and visitors; maximizing physical distancing as much as possible; continuing comprehensive sanitizing efforts, including frequent hand washing; upgraded air filtration systems; and collaborating with health partners and agencies to support free COVID-19 vaccination.

“Ultimately, the greatest protection against COVID and the Delta variant is vaccination,” L.A. Unified said in its statement Thursday. “We encourage everyone who is eligible to be vaccinated.”

The district rolled out an ambitious campaign in May to vaccinate 12- to 15-year-old students before the start of the summer, with schools that had more than 30% of students vaccinated getting $5,000 for projects at their school.