The head of a powerful national teachers union told members Tuesday that its leadership would support "safety strikes" if health precautions are not met amid calls for schools to reopen as coronavirus cases surge. Randi Weingarten, who leads the American Federation of Teachers, is leaving the final decision to local unions on whether to strike. The AFT — the nation's second-largest teachers union, with 1.7 million members — also unveiled several benchmarks that it said should be met before schools can fully welcome back students and staff.