On a roadway with three or more lanes, you must stop for a school bus with flashing red lights:

In general, you must stop for a school bus that is flashing its red lights, whether it is on your side or the opposite side of the road. However, you are not required to stop if the bus is traveling in the opposite direction on a road that has three or more marked traffic lanes, or that is divided by a median or physical barrier.
DMV Writen Test