In most of the United States, drivers on divided highways are not required to stop for a stopped school bus on the opposite side of the highway, according to AAA. Drivers generally must stop for a school bus on a road that is not divided.
Wikipedia notes that if an alternating, flashing red light is displaying on a school bus, drivers approaching the bus from either direction must stop. Drivers must wait to continue driving until the bus again begins moving or until the red light is off.
States that require drivers to stop for a school bus on a divided highway include West Virginia, New York and Arkansas, Wikipedia reports.