You have stopped behind a school bus with its red lights flashing and its stop arm extended. When can you pass the bus?

You must stop at least 10 feet from a school bus whose red lights are flashing and whose stop arm is extended. You must remain stopped until the red lights stop flashing and all the schoolchildren who left the bus have reached places of safety. Note: The Pennsylvania Driver's Manual claims that you must also wait until the bus's stop arm has been retracted, but the relevant Pennsylvania law makes no mention of this. [School Buses, Special Circumstances and Emergencies, Chapter 3: Learning to Drive, Pennsylvania Driver's Manual], [75 Pa. C. S. § 3345]