A primary school in Essex, which has been at the centre of an 18-month battle by parents against academisation plans, has finally been taken out of local authority control and transferred to an academy trust.

Waltham Holy Cross primary school in Waltham Abbey was handed over to NET Academies trust at midnight on Thursday, despite opposition to the choice of sponsor and a last-minute intervention by the local Conservative MP.

The school was ordered to become an academy after it failed an Ofsted inspection in December 2017. Since then it has been the scene of strikes, protests and marches, as parents and teachers joined forces in a campaign that has raised awareness and increased scrutiny of the forced academisation process.

Eleanor Laing, the MP for Epping Forest and deputy speaker of the House of Commons, this week referred the case to the parliamentary ombudsman and wrote to the schools minister, Lord Agnew, asking him to put the conversion on hold pending further investigation.

Agnew said: “Waltham Holy Cross is being converted to academy status to receive the support of a sponsor because it was rated inadequate by Ofsted. We will not stand by idly and see children’s futures damaged by poor education.” Laing, who is in the running to take over as Speaker following John Bercow’s retirement, has been contacted for comment.

A NET Academies trust spokesperson said: “NET has a strong record of improvement within the schools we lead and we will work tirelessly every day to raise standards at Waltham Holy Cross primary. We are excited about being part of this new chapter in its story, starting today [Friday], and we hope everyone will now come together to support that aim.”

Quick Guide Forced academisation of schools Show What is forced academisation? “Forced academisation” describes how a state school in England is compelled to change its legal status from a school overseen by a local authority to that of an academy, and to accept new management by an academy trust. How is it triggered? Forced academisation is an order issued by the Department for Education (DfE). A school is forced to become an academy if it is “eligible for intervention” under law. The order is triggered by a school being classed as inadequate by Ofsted. Previously it could also be triggered by poor performances in exams but that condition was dropped by the education secretary, Damian Hinds, in 2018. Do parents get any say in the matter? No. Governing bodies, parents and councils get no input in the DfE’s intervention to force academisation. They also have no say in which trust the school is forced to join, meaning the chain may be based hundreds of miles away. Critics say this is a derogation of local democracy. What happens to the school? The school’s legal relationship becomes a contract between the trust that manages it and the DfE, cutting ties with local authorities. The school’s land and buildings are effectively leased to the trust. Head teachers are stripped of their autonomy, with budget and staffing decisions made by the trust. In most cases the school’s existing leadership is dismissed. The school’s governors lose legal responsibilities, and there is no requirement for trusts to consult with parents. Often the school is renamed and a new uniform adopted. The trust retains a proportion of the school’s funding for its administration and executive costs. Does forced academisation improve schools? There is little evidence either way. Previously, three-quarters of schools rated as inadequate by Ofsted later improved without forced academisation. The National Audit Office has concluded there is a lack of capable Mats able to improve schools in difficulty.

Some parents have said they will continue to fight. A community petition has gathered more than 1,000 signatures from people opposed to the transfer. Parents say their school has improved since the Ofsted inspection and are concerned about the incoming trust’s record. A report by the Education Policy Institute last year rated NET among the lowest performing school groups at primary level.

Some parents are also dissatisfied with an investigation into allegations of irregularities in the conduct of key stage 1 Sats tests at Waltham Holy Cross. An external moderator from Essex county council raised concerns about the level of “scaffolding” by teachers who were using planning materials supplied by the incoming trust, raising concerns that pupils had been given too much help for their work to be judged independent.

The government’s standards and testing agency was called in but, according to parents, while the Standards and Testing Agency investigated other NET schools, Waltham Holy Cross was investigated instead by an official from the Department for Education which was responsible for the original academy order.

NET denied the allegations and the investigation found no evidence of wrongdoing. “So much has been said about our team over the last few months that has been wrong, unfair and hurtful, and it would have been easier at times to withdraw from the process,” a trust spokesperson said. “But our guiding principle is to help children get a first-class education so that they are able to live their best lives, and we never want to give up on that.”

The school is currently closed for half term, reopening on Monday. Kelly Cross, a parent, said: “It is worrying that ministers are pressing on with this controversial conversion while another MP in their own party is referring them to the ombudsman.”

Another parent, Jay Tailor, said: “It’s a difficult time. We are all concerned and worried that if NET come in the whole ethos and culture of our school will change. Teachers will leave, and what will they be replaced with? It’s not that we don’t like change. It’s just we can see the improvements already, so why are we doing this?”

The National Education Union said it was saddened by the forced academisation. “Concerns were expressed about the fairness of the original judgment on the school by Ofsted. The DfE, for ideological reasons, were intent on forced academisation,” a spokesman said.