Judge MacKenzie said one of the aggravating factors was the impact the offending had on the victim, who had tried to commit suicide.
"I have received and read a very sad and compelling victim impact statement. This offending has had a significant life-changing impact on this young boy," Judge MacKenzie said in sentencing.
"He tried to commit suicide and it is but for his parents finding him that it was not successful. He has had behavioural consequences as a result of this offending. It seems that he has got huge psychological scars and he is struggling to make sense of his world at this particular point in time."
Judge MacKenzie said the victim was angry and destructive and a statement written by one of his parents said the victim embarked on a downward spiral after the suicide attempt.
"One can only hope that in the future he is able to move on and get over this, but you do need to understand that your actions have had a life-changing and devastating effect on this young teenager, especially at a time of his life where teenagers struggle with their emotions and behaviours."
Judge MacKenzie started with a sentence of 18 months but reduced the term because of mitigating factors, including previous good character, remorse, acceptance of responsibility and self-referral for help.
Where to get help
■Lifeline: 0800 543 354 (available 24/7)
■Suicide Crisis Helpline: 0508 828 865 (0508 TAUTOKO) (available 24/7)
■Youthline: 0800 376 633
■Whatsup: 0800 942 8787 (Mon-Fri 1pm to 10pm. Sat-Sun 3pm-10pm)
■Depression helpline: 0800 111 757 (available 24/7)
■Samaritans: 0800 726 666
If it is an emergency and you feel like you or someone else is at risk, call 111.