A St John spokesman said one ambulance and one first response unit attended the incident.
The boy was taken to Middlemore Hospital emergency department. A Counties Manukau DHB spokeswoman said the boy would go home tonight with a repaired laceration.
A group of kids were standing nearby when the incident unfolded.
They told the Herald it appeared a number of boys had been playing around when one jumped and fell on a fence at the school.
The group said they heard someone say the boy, who appeared to be under 10, was "stuck" on the fence.
However, they were unable to get close enough to see exactly what had happened.
Another witness told the Herald it was just a case of "boys being boys" and that the injured child would likely be fine.