The victim suffered serious head injuries when he was assaulted at the entrance to the travelling fair, on Knavesmire Road, near York Racecourse at around 10pm on Saturday 17 September 2011.
He remains in a critical condition in Leeds General Infirmary.
Officers have arrested an 18-year-old man and a 15-year-old youth, who are both from York, in connection with the incident. The 18-year-old has been released on conditional bail and the 15-year-old remains in police custody for questioning.
Despite the arrests, investigating officers are still appealing for information about the incident and are urging witnesses to get in touch with the police or Crimestoppers.
Detective Chief Inspector Keith Ruff, the Senior Investigating Officer, said:
This was a serious assault which has left a teenaged boy fighting for his life in hospital.
We believe that the incident occurred around the time the fair was closing at around 10pm. There must have been people in the area at that time and I urge anyone who witnessed the assault or has heard anything about the circumstances to call the police or Crimestoppers and tell them what they know.
Anyone who can help the police with their enquiries is urged to contact York CID on 0845 60 60 24 7, quoting reference number 12110158476.