A parent has been given permission to go ahead with a legal challenge to the government's policy of replacing schools with academies.
Tamworth Manor campaigners protested at the proposed takeover
Rob Macdonald, from south-west London, is seeking a judicial review of Merton Borough Council's plans to convert his son's school, Tamworth Manor.
Mr Macdonald's lawyers argued in the High Court on Wednesday that the consultation process was flawed.
The council says only an academy can transform educational standards.
On the eve of the hearing, an independent schools adjudicator approved its plan.
Tamworth Manor's intended sponsor is Lord Harris of Peckham, who already sponsors other academies and specialists schools.
Mr Macdonald brought the court challenge on the basis that parents did not have access to the "funding agreement" underpinning the deal.
This contains legal obligations on key areas such as exclusions, provision for special educational needs and admissions.
He admitted his son's school had been struggling, but said parents "did not deserve to lose control" of their local schools.
"I don't believe putting schools into private hands is a step forward, I think it's a step back," he said.
The Tamworth Manor case is the first of three legal challenges by parents' groups opposing academy proposals.
Underpinning them are objections to what people regard as schools being handed over to business people.
Academies are independent state schools with outside sponsors who put up about a tenth of the cost of conversion in return for control of the school's governing body.
The government argues that academies are popular with parents - and there are other parents in Merton who support the academy proposal.
In fact sponsors are a mix of wealthy individuals, companies, education organisations and faith groups.
In Merton, the academy scheme relies on the conversion of two schools, the other being Mitcham Vale High School where the sponsor is the Church of England working with the not-for-profit organisation the Centre for British Teachers and the charity Toc H.
On Tuesday, the Office of the Schools Adjudicator approved the proposals.
Adjudicator Peter Matthews said they provided "at this stage the best opportunity for improving secondary education in this part of Merton".
"They should lead to higher standards and provide a better deal for young people and their parents as well as adding to the diversity of provision in the area," he said.
His office noted that he had taken into account statutory guidance which includes a presumption to approve the closure of a school that is to be replaced by an academy.
A Department for Education and Skills spokesman said an academy was "the best option for local children".
He added: "Academies will offer new opportunities where other intervention and improvement strategies have failed.
"The alternative is for these children to go on being failed and that is not acceptable."