One person was injured when a group of teenagers were interrupted throwing flour and toilet paper over Rotorua Lakes High School.
The school posted on Facebook to say the prank had gone "badly wrong" after they were "intercepted".
A police spokesman said the group was interrupted by a staff member and their son, who was left with minor injuries as the group fled in a silver VW Passat.
The staff member's son required hospital treatment for his injuries.
The school said there would be damage to the vehicle's wing mirror and bonnet as someone had been run over as the group of four fled.
Police were told about the incident about 10.35pm last night.
"Police are appealing for any information about the vehicle, which likely sustained some damage to the driver's side mirror during the incident."
The school is also asking anyone with information to contact them to speak with the principal.
"If you were involved, do the right thing and take responsibility."
It said the incident could have "so easily been so much worse".
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