The spokeswoman said students at Taratahi had been offered counselling and support.
Police were continuing their investigations into the incident.
Detective Peter Donaldson said police responded to a report of an assault at the training centre at 5.15pm.
The victim, a student at the rural job training centre, suffered moderate injuries in the alleged attack.
Donaldson said police spoke to witnesses and made three arrests last night.
A 16-year-old male and two males aged 17 have been charged with common assault. The trio were to appear in the Youth Court next week.
The centre is regarded as New Zealand's largest agricultural training centre. Students live on site at its Masterton campus.
It offers full-time courses, diploma programmes, short courses and a schools programme to help students into a rural career path.