The 11-year-old boy was strung up on climbing bars in the gym at the Hayling School, Hayling Island, near Ports-mouth, Hampshire.
He was discovered choking on the blue and yellow striped tie by a cleaner after being left to fend for himself by his tormentors.The youngster's feet were not touching the ground.
The cleaner released him and he was taken to Queen Alexandra hospital, Cosham, suffering from neck injuries.
He was discharged after treatment and was recovering at home last night.
Detective Chief Inspector Nick Imber, of Hampshire police, described the incident as "a nasty attack of bullying that could have had tragic consequences".
Derek Holmes, the school's chairman of governors, said: "Any incident which affects children in this way is obviously very serious and I'm sure it will be treated very seriously."
The school was the subject of a harsh report by a government inspector last year. The report criticised the way the school was run and expressed concerns over health and safety issues.Reuse content