While riding on a school bus, if a student sustains an injury due to movement of the bus, this is known as:

The term "school bus accident" is appropriate in this context as it refers to an unforeseen event that results in injury or damage, typically occurring due to the movement of the bus. This classification captures a range of scenarios, such as sudden stops, swerves, or other movements that could lead to a student being injured.

Accidents generally imply a lack of intention to harm and usually involve some form of unexpected event, which aligns well with the nature of a student being injured while riding on a moving bus. The concept of an accident encompasses not only collisions but also other situations resulting in harm during normal operation, which is why this term is most fitting for the described scenario.

The other terms do not fully capture the nuance of the event: "school bus incident" might refer to any occurrence without specifying injury, "school bus injury" focuses solely on the result (the injury itself) rather than the event causing it, and "school bus emergency" typically involves a situation requiring immediate action but does not necessarily describe the nature of an injury resulting from the bus's movement.