SAN FRANCISCO, CALIFORNIA - MARCH 18: An aerial view of the empty schoolyard at Ulloa Elementary School on March 18, 2020 in San Francisco, California. As millions of Americans shelter in place in an attempt to slow the spread of the coronavirus, schools across the country are being closed. Nearly 99 percent of the schools in California are currently closed and it is unclear if they will be able to reopen before the start of summer break.