One of the country's top state schools has told 45 students to leave after their parents cheated to get them enrolled.
And Auckland Grammar School says several more will lose their places in its crackdown.
The cheating was discovered by a fulltime enrolments registrar, appointed in February to investigate cases of parents providing false information to get their sons into the school.
Grammar's figures are up on previous years - in 2005, nine students had to leave, as did six from 2003 to the end of 2004.
The Ministry of Education has recorded 13 similar cases at other Auckland schools this year.
Auckland Grammar headmaster John Morris said: "The board are implementing the enrolment legislation rigorously and families who have got in by cheating are being asked to take their sons away. We don't know if it's the tip of the iceberg, but the numbers we are finding are worrying."
Most students were from Years 9 to 11.
"Most are juniors, because ... if they've got through to seventh form now they've got A-level exams in a couple of months' time and it's a bit tough on the kids.
"We do feel sorry for the boys. There is nothing worse than telling a boy who has been at the school for two or three years they have to leave because their parent cheated to get them in. It's not their fault - it's just the families'."
Mr Morris said several Year 11 students in their first year of Cambridge International Examinations were affected and some might have to go to private schools because most state schools did not offer the Cambridge system.
Many of the students were still at the school while appeals against their eviction were heard.
The ACG group of private schools said their Senior College and Parnell school had taken in at least four students from Auckland Grammar at the start of term 3.
A Ministry of Education spokesman said 21 appeals had been lodged, of which three had already been declined.
Mr Morris said some pupils had cheated the system for years but the school's roll of 2500 had made it difficult to find out without a fulltime investigator.
"We now have someone with the time to go around and find out who is living where, and why it seems three families are living in the same address.
"There is no doubt the situation is getting worse."
Under the Education Act, schools can annul an enrolment that is based on false information or if the student uses a temporary residence to enrol.
Any family renting in the Auckland Grammar zone must have a fixed-term rental agreement of at least 12 months. The school refuses to accept students living in homes on a periodic tenancy.
Enrolments can also be annulled when students' enrolment forms falsely claim they are living in the school's zone, or are entitled to priority by falsely claiming to be siblings of other students.
Other schools said rigorous pre-enrolment and enrolment checks kept their annulments low.
Epsom Girls Grammar principal Annette Sharp said her school annulled enrolments only occasionally.
She said it checked family addresses before enrolment and throughout the year.