A fight between Year 9 students at Hutt Valley High School was "frankly appalling", the principal says.
Four students have been suspended after the fight on Monday, principal Ross Sinclair told Fairfax.
Footage of the fight was posted online. It showed students kicking the victim on the ground and hitting the victim from behind.
"What occurred was simply totally unacceptable in any school ... the authorities are involved, there is quite a process running," Sinclair said.
He said he would speak to the school at assembly about the assault, and what was happening more widely in the region.
"As a school community we feel deeply let down by the actions of individuals that are just totally unacceptable."
It has so far been an unimpressive week for schools in the Wellington region, with Wellington College making headlines for its students' derogatory online comments about women, and St Patrick's Silverstream students getting suspended for inappropriately filming female staff.