ORANGEVILLE, ONT. -- Select health units across Ontario are making the call to close schools and opt for remote learning. School boards in Peel Region, Toronto and now Wellington-Dufferin-Guelph have shifted temporarily to online learning while the Ontario government maintains classrooms are safe. Teachers in the Upper Grand District School Board prepared students to return to virtual learning starting Wednesday. Wellington-Dufferin-Guelph's medical officer of health, Dr. Nicola Mercer, said she issued the order for schools to close Monday night after seeing data from the past six days. "We've had nearly 300 cases since Thursday. We closed more classrooms in one day than we did at any time in the pandemic. What we saw, also, was our seven-day rate of cases quadrupled," Mercer said.