More children are attending the country's poorest schools while the number of students at the wealthiest has fallen.
Provisional Education Ministry figures show 8000 more students in decile 1 schools and 20,000 fewer in decile 10, due to a recalculation of school deciles that took effect this year.
The ministry estimates there are about 100,566 children in the wealthiest schools, down from 120,583 last year.
The drop is the biggest on record and means the percentage of children in decile 10 has fallen from nearly 16 to 13.5 percent.
It appears to have happened because some big schools that were decile 10 last year have since been judged to be in a lower decile, while other smaller schools have taken their place.
The increase in decile 1 enrolments is the biggest since records began in 1996, and the first since 2002, taking the number of children in decile 1 schools to more than 60,621, or eight percent of the school roll.
The figures are estimates and do not include enrolments at most private schools.
They show particularly large changes in Auckland, where the number of children in decile 10 schools has dropped by a third to 42,876 and the number in decile 1 has jumped 28 percent to 35,938.
Schools are allocated a decile based on their share of children from the most deprived neighbourhoods calculated using measures including household income, parental education and overcrowding.
About a third of schools moved up the deciles this year as a result of last year's recalculation, a third moved down and a third had no change.
The deciles are allocated so there is roughly the same number of schools in each, but the size of the schools varies.
Though about 10 percent of schools are in decile 1 , only eight percent of students are in that decile.