Biden selects Kamala Harris as running mate, some schools are already flunking COVID-19 safety tests, and late civil rights activist Mimi Jones on fighting for justice in the pool.Watch NBC Nightly News With Lester Holt at 6:30 p.m. ET 5:30 p.m. CT (or check your local listings).00:00 Intro01:32 Biden Picks Kamala Harris As 2020 Running Mate05:16 Trump & GOP React To New Biden-Harris Ticket07:30 900 Students, Staffers Quarantined In Georgia County08:26 Cases Surge 130 Percent Among Florida Kids In A Month08:57 Teacher Blast New York's School Reopening Plan11:43 Big Ten, Pac-12 Postpone Seasons Due To Coronavirus11:58 Putin Claims Russia Has Developed First Covid Vaccine14:39 Teen Vaping Dramatically Raises Risk Of Covid-1917:06 Severe Storms Cut Path Of Destruction Across 9 States