At 50.4 meters, there was good evidence that Mr. Ashir's vehicle had not yet passed the property line and thus had not yet left the zone. Had he passed the school grounds, he'd have passed the school zone. Besides, that case was about pro-d days, not signage placement.
Looking at Google Earth, at 50.4m he's barely into the block the school property spans
http://imgur.com/g9WwDAH
So if I'm on a highway with a speed limit of 80km/hr, but the oncoming traffic has a speed limit of 90km/hr, the speed limit signage for the oncoming traffic also applies to me?