Banking blogger Michael Reddell has turned his glare onto school fundraising, accusing his daughter's school of "compulsory conscription" for a "staggeringly uneconomic" market day.

A former top economist has accused his daughter's school of using "child conscription" to run a "staggeringly uneconomic" market day.

Michael Reddell, a former special advisor to the governor of the Reserve Bank of New Zealand, has written an acerbic blog since he was made redundant from the central bank in 2014.

Many of his posts - which are widely read in political and financial circles - target his former employer, but on Thursday he fired a shot at South Wellington Intermediate School, the day of its annual market day.

Maarten Holl South Wellington Intermediate School principal Traci Liddall says Reddell had the "wrong end of the stick" on the market day, arguing the event helped learning in a number of areas, from social studies to financial literacy.

The school has responded that Reddell misses the point of the event.

READ MORE:

* Senior Reserve Bank officials accuse former colleague of having a 'victim filter'

* MediaWorks admits leaking Reserve Bank of New Zealand interest rate decision

* Reserve Bank of NZ conducting probe into alleged leak of OCR decision on March 10

* Not in NZ's 'economic interests' to release interest rate votes - Reserve Bank

Reddell has previously argued that it would be more efficient for parents to simply write a cheque than take part in school fairs, but this was not an option for him.

"My daughter's intermediate school (as left-leaning as they come) practices a much more inherently exploitative and costly fund-raising model," Reddell wrote.

"[H]ow is this money raised? By the compulsory conscription of the children. The kids have no choice about being involved: more-structured teaching is simply set aside to make space for all the time "market day" involves.

"Kids are encouraged to beg for money ("seek sponsorship") from local businesses.

"Now some of the kids seem to quite enjoy what they are doing, but that isn't really the point. And outside North Korea, it isn't how real businesses operate either."

Reddell said based on the accounts of his children he believed around a week per child was spent preparing for the market.

Calculating that this equated to around $400 per child, with 250 pupils this meant $100,000 of school time went into the market day.

"And in addition to the $100,000 of lost (well "stolen" would be more accurate) time there are all the donations of ingredients from parents - again something over which we had little effective choice - and the donations from local businesses," Reddell wrote, adding that he doubted the event raised $20,000.

"It is just staggeringly uneconomic - and has me looking less unfavourably on old-fashioned school fairs."

This, Reddell argued, was not the right way to run public services.

"Perhaps the Air Force could plough up all that land at Ohakea and send their staff out to work each day growing turnips, grazing sheep or whatever to supplement their budget...Perhaps Treasury could run cake stalls on The Terrace each lunchtime to help cover their costs?

"But even that would be less bad than compulsory stealing the scarce learning time of our children to, extremely inefficiently, raise funds to keep schools going."

South Wellington Intermediate School principal Traci Liddall said Reddell missed the point of the evening.

"Doing some fund raising is a by-product of the learning. There is no way my staff would even consider the huge amount of work if it was just about making a little bit of cash," Liddall said, with the lessons from the event broad.

"It covers all of the key competencies. That's thinking, using language, symbols and text, managing self, relationships to others, participating and contributing, all of that is covered, Liddall said.

"We have a whole financial literacy unit build around the evening."

She denied the pupils asked for money, requesting instead goods and services for creating products for the market day.

"The comment [Reddell makes] that it's not how a real business works; actually, we're considered a charity, and that's exactly how charities work," Liddall said.

"His focus is on the money making. That's not the focus of market evening, that's an outcome but it's not the focus."

Asked about whether the event raised the up to $20,000 Reddell speculated, Liddall said: "I wish."

Reddell was "an interesting parent" who Liddall dealt with "on a fairly regular basis".

Since leaving the Reserve Bank Reddell has become something of a thorn in the side, criticising a series of decisions and policies.

He also led to a substantial change in the way the Reserve Bank communicates, after revealing that he had been leaked an interest rate decision ahead of its official release.