Pupils at Kurri Kurri High School watched in horror as the spike penetrated the 15-year-old girl’s right forearm close to her elbow.

Ambulance officers from Kurri Kurri treated the girl and placed a box under her feet to take the weight off her arm.

Then the fence was cut away and the girl’s arm was freed.

She was loaded aboard a Westpac rescue helicopter and flown to Newcastle’s John Hunter Hospital in a stable condition.

The incident happened shortly after 11.30am when the girl slipped while climbing the 3m metal fence, bystanders told the Mercury.

An ambulance paramedic at the scene told the Mercury: “One metal spike went through the girl’s underside right forearm, close to the elbow.

“The spike penetrated fairly deeply – up to 10cm – but it did not come out the other side of her arm.

“The girl was given drugs to reduce the pain and to calm her.

“Then workers’ tools were used to cut the fence and free the girl.”

Intensive care paramedics loaded the girl onto the Westpac rescue helicopter in a stable condition, the paramedic said.

An education department spokesman said: “The Year 9 girl was trying to climb over the fence during lunch break.

“Her mother was immediately contacted and a teacher was on hand a few second later to support the girl and prevent further injury.

“The girl suffered no major bone or blood vessel damage.

“Counselling has also been made available to pupils who witnessed the incident and to anyone else who knew the girl and may need it.”