Why must a school bus driver use and properly adjust the bus's mirror system before each route?

A school bus has a system of mirrors — flat outside mirrors for distance behind, convex mirrors for a wider view along the sides, and crossview (crossover) mirrors that let the driver see directly in front of and beside the bus. Together they cover the danger zones where children walk and where direct vision is blocked. The driver must adjust all mirrors before driving so the required areas are visible, and use them constantly when students are loading, unloading, or crossing. A child in the front danger zone can only be seen in the crossview mirrors, so proper adjustment and use are essential to avoid striking a student.