What is the maximum tail swing distance a school bus can have when making a turn?

AAMVA CDL Manual, Section 10.7.4 (Tail Swing), p. 10-11

Tail swing means the back of a school bus can swing outward in the opposite direction of a turn, even after the front of the bus has already cleared an obstacle. A driver who doesn't account for this can strike a parked car, a pole, or a student standing near the curb without ever seeing it happen from the front of the bus. Knowing the three-foot figure and checking mirrors throughout the turn, not just before it, is what prevents this type of crash.