"It was based on socio-economic data at a school board level or the area that they were based in, and it looked at income levels, the number of people on benefits, household crowding and those kinds of factors," Neilson says.
"The schools were then ranked into 10 different deciles, with one being the lowest and 10 being the highest."
The problem with the system was that it was not sufficiently nuanced to give an accurate reflection of what was actually happening in society.
"It was based on these five broad factors and it was not individualised," says Neilson.
He explains that factors like house prices and income would distort the decile rating of schools in urban areas by not taking full account of the real socio-economic situation of the area.
"You had these mismatches of data, and then the ranking system also led to a bit of stigma towards schools. People were misinterpreting it as a measure of educational quality and even deterring some students from going to those schools."
Making the system even more problematic was the fact that it was based on Census data, which by now is completely out of date.
"This new system takes advantage of all the latest data we have ... It takes the Stats NZ database, which pulls together data from across all different government departments," says Neilson, explaining that this data is updated far more regularly.
Given the need for improving the system, there has been cross-party support for the changes.
"National first started work on these changes, so the other large party in Parliament is supportive of this," says Neilson.
While the support for the new system is there now, Neilson says it will pay to keep an eye on the roll-out next year.
The execution of the new system will ultimately determine how well it is received.
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