The head prefect of Wellington College says schools have valid reasons for monitoring internet postings by students.
The Secondary School Principal's Association says Twitter, Facebook and Youtube are regularly checked by most schools after tip-offs from parents, students and others.
The aim is to curb bullying and truancy, and to look for breaches of school rules or criminal activity.
While some teenagers spoken to by Radio New Zealand are unhappy with the practice, Wellington College head prefect Rayhan Langdana endorses it.
He says it might force students to be more careful and to realise they cannot get away with posting inappropriate comments or videos.