You must stop for a school bus:

You must stop when approaching a school bus that is displaying flashing red lights while stopped to pick up or drop off children. On a two-lane road, traffic moving in both directions must stop and remain stopped as long as the red lights near the top of the bus are flashing and/or the stop arm on the left side of the bus is extended.

• That is parked on the shoulder of the road with no one in it.
• When it approaches you, even if its lights are not flashing.
• If you are both driving on a two-lane highway and its red lights are flashing.
• Whenever the driver waves at you.