Crossover mirrors, mounted at the front corners of a school bus, are specifically designed to show the driver which area?

AAMVA CDL Manual (nhcdm.pdf), Section 10.1.5 – Outside Left and Right Side Crossover Mirrors, p. 10-2

The front danger zone directly in front of a school bus is exactly where a small child is most likely to be and least likely to be seen without a crossover mirror — this is the mirror most directly tied to preventing a dart-out tragedy at the front of the bus.