When Neville Wall found seven "tinnies" of cannabis in his son's bag, he was so concerned and frustrated he put him in a headlock for discipline.
But he applied too much pressure and broke blood vessels in the boy's eyes.
Wall, a 36-year-old bushman, was sentenced in RotoruaDistrict Court yesterday to a year in prison after pleading guilty to a charge of injuring his 13-year-old son with reckless disregard on June 2.
The boy's injuries weren't picked up until about a week later when his school contacted police concerned about his red eyes.
The injury, known as subconjunctival haemorrhage, is linked with strangulation.
But Judge Cooper recognised the injury didn't result in any long- term damage.
His lawyer, Ian Farquhar, told Judge Phillip Cooper Wall had handed back his gang patch and was making an effort to provide a better life for his family - which included seven children.
Judge Cooper said the offending was aggravated by the fact he was on bail at the time on a charge of assault with intent to injure.
That charge related to an incident in April when he punched a woman in the face and shoulder.
Judge Cooper said he recognised Wall was upset with his son's actions and the fact he had been getting mixed up in gangs.
Wall was sentenced to 12 months for the assault on his son and is to serve an additional four months for assaulting the woman.
