An 11-year-old boy is in Auckland's Starship Hospital after he became impaled on a steel spiked fence at school this morning.

The boy was at Liston College in Henderson, west Auckland, when he fell onto the school's perimeter fence and was impaled through the knee by a steel rod.

A man on a ladder took his weight while efforts were made to cut through the rod with a hacksaw before the arrival of firefighters who used the jaws of life to cut him free and he was taken to hospital with the rod still embedded in his leg.