PHILADELPHIA (CBS) — The Philadelphia School District is preparing for the return of students to full in-person learning on Aug. 31. On Thursday, the school district showed off air purifiers that will be placed in all schools.

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“These air and surface purifiers use NASA-based active plus pure technology, which eliminates 99.9% of airborne SARS-COVID2 viruses and come in various sizes depending on the area of the space that they are to be used,” Philadelphia School District COO Reggie McNeil said. “When tested in an in-close setting, the air purifying technology deactivated the virus to below detectable levels in three minutes.”

In addition to the air purifiers, the district said cleaning and sanitizing will continue.

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Meanwhile, Thursday is decision day for Pennsylvania parents with school-age children. They have to decide whether they want their children to repeat a grade.

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Under new Pennsylvania law Act 66, students enrolled this past year can repeat. The intent is to allow students to make up for any educational opportunities lost because of the pandemic and remote learning.