The Government's flagship fees-free policy appears to have seen a rise in high school students from wealthier neighbourhoods going to university, according to data released under the Official Information Act.
But the Tertiary Education Commission, which released the numbers, says that care should be taken in interpreting the data.
Labour had hoped that the fees-free policy would help those struggling to afford tertiary education, but the National Party has criticised it as helping students from wealthy families who would have gone to university anyway.
• Premium - Generation Debt: Will fees-free tertiary education change lives for a new generation?
• Up to $50 million paid for fees-free students who either failed or withdrew
• 41,700 sign up for fees-free study, but total numbers are falling
• Premium - One third of fees-free students fail or withdraw from course
The Herald requested a breakdown of 2018 fees-free students by decile compared to previous years, and the commission provided a comparison with a similar group of 18- and 19-year-old students in 2017.
There were about 42,231 fees-free students in 2018, and 35,773 students in the 2017 comparison group.
According to the data, fees-free appears to have boosted the proportion of decile 6 to 10 students going to university, while the proportion of students from decile 1 to 5 schools attending non-university tertiary study fell.
Excluding students where the decile was unknown, decile 6 to 10 students made up 68 per cent of fees-free students, up from 62 per cent from the 2017 group.
• 55 per cent of fees-free students went to university in 2018, while 28.5 per cent went to Institutes of Technology or Polytechnics (ITPs), 16 per cent to private training establishments (PTEs), and less than half a per cent to wānanga.
• In the 2017 group, 45.5 per cent of comparable students went to university, while one third went to ITPs, 20 per cent to PTEs, and 1.7 per cent to wānanga.
Education Minister Chris Hipkins said he was "largely happy" with how fees-free was tracking and it would take time to see any real behavioural change.
He also noted that the data excludes apprentices.
He said if National wanted to means-test fees-free, it should tell parents.
National wants to scrap fees-free and has floated ideas about where to put the billions of dollars it would save, such as an Education Saver account.
National's tertiary education spokesman Shane Reti said the data showed that fees-free was middle-class welfare.
"Universal application of fees-free fails to most help those who most need it."
Act leader David Seymour, whose electorate of Epsom is not short of high decile schools,
said that parents had told him: "My kid is going to get this benefit. They don't need it."
He pointed to a Weekend Herald investigation last year that found only one in 100 entrants to elite university courses came from the most deprived homes.
One university took only one decile one entrant - out of more than 2000 - into its engineering programme in five years.
"The overall approach the Government is taking is that they're not doing enough to ensure that lower-decile students have a chance to get to the starting line," Seymour said.
"Meanwhile they're throwing more money at the students already at the starting line. If you're long-goal is to be more equitable, that's not going to help."
Tertiary Education Commission chief executive Tim Fowler said that care should be taken in drawing any conclusions from the decile data.
"This is because the TEC only holds information about the decile rating of the school a learner attended for approximately 80 percent of learners.
"As deciles relate to the overall socio-economic status of the school, it may not reflect the socio-economic status of a particular learner.
"In addition, not all students in the tertiary education system attended a New Zealand secondary school or may not have specified their last school attended when they enrolled at a tertiary provider."
The Government is planning to abandon the decile system in favour of a equity index in 2021 or 2022.
Previous data released under the OIA showed that fees-free students were more likely to be NZ European, and more engaged in university-level study than non-fees-free students.
Fees-free students last year were 68 per cent NZ European, 17 per cent Māori, 12 per cent Pasifika and 15 per cent Asian.
Non-fees-free students in 2018 were 63 per cent NZ European, 21 per cent Māori, 9 per cent Pasifika and 15 per cent Asian.
OIA data also revealed that a third of fees-free students either failed or withdrew from at least one of their courses last year.
The TEC did not have details on how much the Government had spent on courses students failed or withdrew from.
But based on the 13,770 students who failed to complete at least one course, and the average course cost of $2800 for Student Achievement Component, the figure could be as high as $40 million.
A TEC spokesperson said that fees-free did not appear to have had a negative impact on student performance, as a comparable group from 2017 showed that 37 per cent of students had failed or withdrawn from a course.
Overall tertiary student numbers dropped from 310,000 in 2017 to 305,920 in 2018, and the 42,150 fees-free students fell well short of the anticipated 80,000 that Labour had expected.
The $200m in savings from the lower-than-expected uptake has been put towards the Government's reforms of the vocational education sector.
Labour's original policy was to extend fees-free to cover two years' worth of fees after 2020, and then three years from 2023, but the Government has not allocated any funding for that.