The School District of Philadelphia is warning parents that it might be forced to revert back to “100 percent virtual learning” if workers providing transportation for students and teachers go on strike. In a letter sent to parents Monday, Superintendent William Hite said that Transit Workers Union Local 234 has voted to authorize a strike. The union’s contract with Southeastern Pennsylvania Transportation Authority (SEPTA) will expire on Oct. 31, meaning that a strike could occur on Nov. 1, if a new contract agreement can’t be reached by then. Some 60,000 Philadelphia students rely on SEPTA for daily commute, as do many teachers and staff members, Hite said, adding that a nationwide driver shortage is already disrupting his district’s operations. “The School District of Philadelphia is not directly involved in these contract negotiations,” he said. “However, it is clear that a SEPTA strike would have a devastating impact on the operation …