As far as I know the bus has to be stopped with the overhead red lights flashing
and the stop sign arm activated/ extended for a conviction. Not that I am condoning blowing past a school bus with its lights on or not exercising the utmost caution when dealing with kids loading or unloading from a school bus. You never know when one of those little guys are going to bolt out of nowhere infront of you.
That being said I think you would hard pressed to find any police officer that wouldn't lay that charge in a similar situation, just because of the potential consequences.
However:
There seems to be several facts that must be met for that charge: The first would be what qualifies as a 'stopped school bus'? According to the definition it would be one that is 1) actually stopped on a highway (not moving). 2) has it's red overhead lights flashing 3) has actuated the school bus stop arm. Refer to sub section (6) below.
Under sub-section 11 it states that a driver "
shall not proceed until the bus moves or ...."
Therefore it would imply that a driver is allowed to proceed when the bus is in motion even if the red flashing lights are active.
So if the bus was still moving and no arm was activated your buddy may have a chance to explain himself. Also someone raised a good point about how far he was from the bus when the lights came on. Those buses dont just turn on the lights, hammer the brakes, and stick the arm out all at once. They usually give fair warning that they are about to stop, hence the section is written regarding school bus driver signals.
Heres the black and white from the HTA:
Duty of drivers when school bus stopped
(11) Every driver or street car operator, when meeting on a highway, other than a highway with a median strip, a stopped school bus that has its overhead red signal-lights flashing, shall stop before reaching the bus and shall not proceed until the bus moves or the overhead red signal-lights have stopped flashing. R.S.O. 1990, c. H.8, s. 175 (11).
School bus driver, signals
(6) Subject to subsection (9), every school bus driver,
(a) who is about to stop on a highway for the purpose of receiving or discharging children or receiving or discharging adults who have developmental disabilities, shall actuate the overhead red signal-lights on the bus;
(b) as soon as the bus is stopped for a purpose set out in clause (a), shall actuate the school bus stop arm; and
(c) while the bus is stopped for a purpose set out in clause (a) on a highway, shall continue to operate the overhead red signal-lights and stop arm until the passengers have been received or discharged and until all passengers having to cross the highway have completed the crossing. R.S.O. 1990, c. H.8, s. 175 (6); 2000, c. 26, Sched. O, s. 14; 2001, c. 13, s. 18 (4).