According to the AAMVA manual, under what circumstances is a school bus driver permitted to back the bus?

AAMVA CDL Manual, Section 10.7.3 (Backing), p. 10-11

Backing a bus full of blind spots around children is one of the highest-risk maneuvers a school bus driver performs, which is why the manual treats it as a last resort rather than a routine option. This question tests whether a driver understands backing is the exception, not a normal part of the route.