The road was wet because of heavy rain and there were intermittent heavy downpours.
Kiel-Bidois failed to see in time that the vehicle in front of him had slowed because of the conditions. He braked heavily, causing his vehicle to slide and, panicking, he applied the handbrake.
His vehicle slid across the centre line onto the wrong side of the road and into the path of the Toyota Hiace van carrying Opotiki Primary School staff who were returning from an end-of-school "pampering" trip to Rotorua.
Eight of the nine people in the van were injured.
One suffered a serious spinal injury and is now a paraplegic. Others suffered injuries including broken bones and fractures, ruptured spleen, lacerations, bruising and ligament damage.
In explanation, Kiel-Bidois told police the car in front had almost stopped in a puddle and he slammed on his brakes, causing his truck to fly towards it.