According to the not-for-profit organisation's projections, Kiwi parents will pay about $16,000 for a child starting their eight-year primary school state education this year.
More than $18,000 will be needed for the same child's secondary school years.
"In the past we have always convinced ourselves that a government education is a free education," ASG chief executive John Velegrinis said. "But not when you actually think about all of the inputs, every time the parents have to put their hand in their pockets."
The cost of education had risen by one and a half times the rate of inflation in the past 10 years, a situation that was unlikely to change, Melbourne-based Mr Velegrinis said.
"Over the last 10 years educational costs as a subset of the overall cost of living index have risen by 1.5 times. They are moving at a faster rate than the general basket of goods and services. We don't see that abating."
While there would be a variation across different decile areas, ASG's figures were an accurate reflection of the average cost for parents, he said.
"The numbers stack up."
While the true cost of a "free" state education will shock some parents, the figure is dwarfed by the average cost of a private education, which ASG puts at $262,310. New Zealand is also much cheaper than Australia, where a comparable education would cost roughly double.
Given the cost of even a state education, ASG advised parents to plan ahead.
"What we are trying to do here is say to parents: 'This is a big thing for you so you need to actually plan."
Mr Velegrinis said measures announced yesterday in the Government's $359 million shake-up of the education system appeared positive.
"One of the things we do know is that the quality of the teaching profession is one of the key inputs to a great education. Anything that supports that, we are really supportive of. We don't necessarily know all of the details but directionally we think it is great."
Parents can find the likely cost of their child's education using an online calculator at asg.co.nz.
Doing the maths
• $35,000 - The average cost per child of a state education in New Zealand, the survey says
• $16,000 - What primary education costs over eight years
• $18,000 - Cost of secondary education
• $262,310 - What a private education will cost - roughly 7.5 times the cost of a state education
