A new private school offering a no-frills education for just £52 a week will open its doors to pupils in Durham this week, despite vociferous opposition from teaching unions, which say it is impossible to provide a quality education on such a low budget.

The launch of the Independent Grammar School: Durham has been greeted with scepticism by many in the sector who accuse the school’s founders of using children as guinea pigs in an educational experiment and trading on parents’ anxieties about finding the right school for their child.

Fees for the new school are £2,700 a year, way below average private school fees of £17,000 and significantly less than the government spends on state schools. In 2015-16, the average primary school in England received funding of £4,900 per pupil per year, while secondaries received £6,300, according to Institute for Fiscal Studies analysis.

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Kevin Courtney, joint general secretary of the National Education Union (NEU), which has campaigned against IGS:Durham, said he fears the school will fail – as the Durham Free School did before it – causing huge disruption and trauma for affected pupils. “I’m really not confident that it will work,” he said. “It’s unbelievable to me that you can run a school on £52 a week per child.”

The opening has been delayed twice, but plans for the school were finally approved by the Department for Education in May and headteacher, Chris Gray, told the Observer the school would be open as promised , though he did not respond to calls seeking further comment.

The controversial school, which is in a refurbished church on a busy crossroads in the city centre, is the idea of James Tooley, professor of education policy at Newcastle University and champion of low-cost private schools in developing countries around the world.

Tooley is the co-founder and chairman of Omega Schools Franchise Ltd, a chain of low-cost private schools in Ghana, and has also helped develop similar schools in Sierra Leone, India and Nigeria. He has said he would like to roll out the low-cost model elsewhere in the north of England, opening a school in Sunderland next year, and five to 10 more in the next few years.

It’s unbelievable to me that you can run a school on £52 a week per child. Kevin Courtney, NEU joint secretary

Tooley has previously outlined his vision for education in England in an interview with the Guardian, saying: “I don’t support Michael Gove’s free schools or US charter schools. I’m a purist. The government shouldn’t privatise education because it will make a mess of it , as it did with the railways. I want to see private schools emerge and then the state just move aside from education.”

Local NEU officials said they believed the uptake of places at the new school has been low, possibly only 22-24 pupils. School activity on social media has been limited to a picture of a shelf of books on Instagram with the comment “At IGS:Durham we love books” posted last week, and a video of someone using a fire extinguisher. In a Daily Telegraph article in July, Tooley – who also did not return calls – said he hoped to recruit 65 children aged four to nine (reception to year four) in the first year, but hoped to develop it into an all-through school. Despite its name, it is not a grammar, is not selective and there is no test to get in. Tooley has sunk his own savings into the project and is now looking for other commercial investors to expand the business. Fees are being be kept down by savings on buildings and IT.

The shadow education secretary, Angela Rayner, described the school’s opening as a sad indictment of Tory education policy. “The fact that businesses see austerity as an opportunity to profit should serve as a wake-up call for ministers about the impact of Tory cuts on state schools.”

A DfE spokesman said: “As this is an independent school, we do not make a judgment on the fee levels it charges – this is the responsibility of the owner. However, we scrutinised the application from the school and Ofsted has also conducted a pre-registration inspection.

“It advised that the school will be meeting the required standards when it opens and it will be inspected during its first year of operation to confirm those standards are being met – if not, we will take appropriate action.”