California School Bus Pre-Trip, presented by Visalia Unified School District Original Trainee 

Not required in most states, but some do require it, also the seats protect the children since they’re close together.

I noticed as well it's suppose to be Left and right flat mirrors adjusted to see 200 feet to the rear of the bus and 1 inch of the bus Left and right convex mirrors are adjusted to see along side the bus, the front of the rear duals on the ground and eliminating blind spots.

It's the flat mirror Convex mirror and the front of the bus are called cross-views