The South Portland School Department will require all students and staff to wear masks in indoor settings this fall.

“We have decided all students and staff members, regardless of vaccination status, will wear masks during the school day or when participating in after-school activities indoors,” Superintendent Tim Matheney said in a video released to families Tuesday. “Masking, we believe, is essential for us to hold firm to our plans for five days per week in-person learning.”

The decision comes as school districts around Maine are determining how to move forward following new coronavirus guidance from the U.S. Centers for Disease Control and Prevention and the state recommending everyone in K-12 schools wear a mask indoors regardless of vaccination status.

The spread of the contagious delta variant of the virus, combined with the fact that only about one-third of students in South Portland are eligible for vaccination, contributed to the decision. In addition, there have been a small number of breakthrough cases among the vaccinated, though the vaccines are highly effective in preventing serious illness.

“For all those reasons we believe it is wise to start the school year with all of us wearing masks,” Matheney said. “We will continue to monitor pandemic data and the guidance of experts like the federal and Maine CDC. We remain hopeful we may be able to move away from the masking requirement once we see significant progress toward the end of the pandemic.”

South Portland is continuing to look at the state’s pooled coronavirus testing program being provided to school districts, but is not currently planning to participate.

“If at any point the pandemic significantly worsens in Cumberland County we will revisit our current decision about pooled testing,” Matheney said.