When approaching a school bus with flashing signals and an extended stop sign, you must stop and remain stopped until:

You must stop for stopped school buses with flashing red lights and an extended stop sign when you approach from any direction on a highway, private road, or school driveway. Stop and remain stopped until all persons are clear and the bus moves again. Even if the signals are not on, you must stop any time a school bus is loading or unloading passengers.