You may pass a school bus from the front or rear on an undivided roadway:
Under no circumstances.
When the red lamps on the school bus are flashing.
When the red lamps on the school bus are not flashing.
At anytime, if you drive slowly.
You may not pass a school bus on an undivided highway from either direction while the school bus is using its flashing red lights. If there are no flashing red lights, you may pass normally.