Stopped School Bus

You must stop for a stopped school bus with flashing lights that is
loading or unloading passengers. This is required by law whether you
are meeting the bus or traveling behind it under the following conditions:
1. On any two-lane highway.
2. On any four-lane or multi-lane highway only when traveling
behind a school bus.
3. When passing a school bus that has red or amber signals

​retrieved from: South Carolina DMV Online Drivers Manual 

When must Stop

Please note that school bus laws can vary from state to state.  The examples below were retrieved from the SC DMV Online Manual as it applies to South Carolina laws and regulations

1. When the bus is in a passenger loading zone completely off the
main travel lanes and when pedestrians are not allowed to cross
the roadway.
2. A driver of a vehicle need not stop upon meeting a stopped
school bus when traveling in the opposite direction on a multilane
highway or multi-lane private road. A multi-lane highway or
multi-lane private road is defined as a highway or private road
that consists of four lanes, having at least two traffic lanes in
each direction.
You must always stop on any highway when you are behind the
bus.When you have stopped, you must not proceed until the bus
moves or the driver signals to you that the way is clear, or the red lights
are no longer flashing.

​​retrieved from: South Carolina DMV Online Drivers Manual 

When you do not have to Stop

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