PHILADELPHIA - The School District of Philadelphia announced virtual classes will be held with teacher-led instruction Tuesday morning and asynchronous independent tasks assigned by the teacher in the afternoon due to a nor'easter bringing heavy snowfall to the area.The district also said all school buildings will be closed Tuesday, including the district headquarters and family technology support centers, to allow for safe clearing of snow from all roadways and walkways."This provides our staff, students and families with the opportunity to find a little time in the afternoon to enjoy some fun, outside activities.