An undated photo provided by Mettie Walker shows Jaleah Walker, a student at Corinth High School in Mississippi. In their first week back, students have faced altered classrooms and emergency quarantines. (Mettie Walker via The New York Times) -- NO SALES; FOR EDITORIAL USE ONLY WITH NYT STORY SLUGGED VIRUS-SCHOOLS-REOPEN BY ADAM WREN and DAN LEVIN FOR AUG. 7, 2020. ALL OTHER USE PROHIBITED. --