A blood sample was found to contain tetrahydrocannabinol - the active ingredient of cannabis.
Morehu had also started work at 4am, resting for less than two hours, and made omissions to his log book.
Three months later, Morehu crashed a car. He was later processed with 165mg of alcohol per 100ml of blood.
Morehu's lawyer, Miharo Armstrong, said Morehu smoked cannabis two days before he crashed into the truck but was not under the influence of drugs at the time.
Morehu could not recall much of the crash except hearing children screaming and emergency services lifting him out of the truck.
Following the crash, Morehu had struggled to cope and resorted to alcohol to mask what had happened.
Morehu, who stared at the floor throughout his sentencing, was deeply remorseful and had met about 27 people from the community last week at a restorative justice meeting where he apologised.
Before these two incidents, Morehu had an unblemished record.
There were more than 30 people in the public gallery including the wife of the bus driver and grandmother of one of the children who was seriously injured. She said in court she was not angry at Morehu and that her grandchild was doing well. However, she said her husband was still going through the ``healing process''.
Judge Robert Wolff commended the bus driver for the way he controlled the bus after it was hit and said he should be recognised in some way for that.
He said there had been requests from some of the victims' families, but not all, for reparation to recognise the emotional harm suffered which made it difficult to quantify how much reparation should be ordered.
Judge Wolff said Morehu, who the court was told had suffered a shoulder injury in the second crash, was receiving ACC and would not be able to afford the amount of reparation that could be imposed.
The emotional harm suffered was "incalculable'', Judge Wolff said.
He said those at the restorative justice meeting did not want Morehu to go to jail.
Judge Wolff told Morehu he could pay back his community by doing work for them and demonstrating he ha learnt his lesson.
Morehu was ordered to pay more than $1000 for the damage to the tractor he crashed into during the second incident and the blood test fees as well as court costs.