A jury of five men and seven women took about 4-1/2 hours to find Redeemed guilty of three charges of manslaughter.
They also found him guilty of two charges of injuring with reckless disregard and one charge of causing grievous bodily harm with reckless disregard.
He was found not guilty of one count of injuring with reckless disregard.
Redeemed, who has "Praise God'' tattooed across the front of his neck, stood impassive in the dock as the verdict was returned.
He had also faced three charges of dangerous driving causing death, which the jury was to consider only if he was acquitted of manslaughter.
Jethro Cooper's father, Max Cooper, said outside the court he was happy with the verdict but "at the end of the day, no one is going to be happy with the outcome. It's not going to bring our kids back''.
"Three kids were wasted needlessly in this stupid act - by an adult,'' he told APNZ.
"I'd still like to grab him by the throat but I shouldn't really say that.''
Mr Cooper had some advice for young people: "Be careful and be aware of who you are in the car with.''
Jethro's mother, Jackie Cronin, said she was happy with the verdict.
"It doesn't change the fact that we've lost our son but it does put this part behind us so we can try and put some sort of life back together for ourselves,'' she told APNZ.
The verdict was what they had hoped for but "we were trying not to think about it too much because if it came back with a not guilty verdict, we weren't too sure how we were going to cope with that''.
Justice Whata earlier today summed up the two key issues the jury needed to consider _ whether Redeemed had turned the wheel of the car, causing it to move into the path of the bus, and whether he was he aware of the dangerous consequences of that action.
Defence lawyer James Rapley yesterday questioned the reliability of the Crown's key witness, Reece Dick-Durham, 18, who was the only passenger in the car besides Redeemed to have survived the crash.
Mr Dick-Durham told the court that Redeemed had leaned over to look at the oncoming bus before grabbing the wheel with his right hand, and steering the car into the other lane.
The defence argued that Redeemed did not grab the wheel of the car and Mr Dick-Durham may have mixed up the crash with previous events in which the car had been driven dangerously.
Mr Dick-Durham may also have mixed up the crash with an account he heard of an earlier incident in which Redeemed grabbed the wheel of another car, after which he said something like: "I could end it.''
Crown prosecutor Claire Boshier said Mr Dick-Durham had a clear recollection of Redeemed taking hold of the wheel because of the danger to him.
Mr Dick-Durham had been asked 13 times under cross-examination whether he was mistaken but he was adamant he was not.
The four-day trial, which heard from 21 Crown witnesses, was moved to Wellington from Christchurch because of earthquake damage to the courtroom.
Redeemed was remanded in custody and will be sentenced in Ashburton on October 25.
