Yes! When they are letting kids off it becomes a defacto crosswalk where kids might come out to cross the street in front of the bus but you can't see them because of the bus itself blocking your view.

Many school buses have stop signs that extend when they have the doors open to help remind people of this and prevent the little overzealous street crossers from getting splattered.

Ah I see thank for the explanation! That makes sense. We don't really get school buses here, kids go to school on the bike or here in the city by metro. (Or the parents drop them off of course).