Police in Auckland are again warning schools of the dangers of student parties involving alcohol.
They have written to principals and school ball committees saying they will take action to stop large after-ball events this ball season.
The letter says there is concern over the level of secrecy surrounding the organisation of after-ball parties.
Inspector Andrew Coster says in the letter that signed permission slips from parents and caregivers have no legal standing.
He says prosecutions may be brought against those who organise large gatherings.
Police first wrote to schools after the death of King's College student James Webster from alcohol poisoning last year.