Up to six police cars were seen outside the school just before midday and officers were patrolling the grounds.
It is not known if the victim is a student or a member of staff.
Principal Jeff Freeman told Newstalk ZB this afternoon that all the children were safe and well and were playing outside.
Freeman has now written to parents, telling them something had happened but not saying what it was.
Police said they would not comment until further enquiries were made.
Source: Hamilton News