Schools that do not convert to become academies are more likely to achieve higher ratings from Ofsted, research suggests.

Findings from the Local Government Association (LGA) showed that 92% of local authority (LA) schools had been rated “good” or “outstanding” by Ofsted since January 31, compared with 85% of academy schools graded since they converted.

In research into Ofsted ratings between August 2018 and January 2022, the LGA found that just 45% of academy schools improved their rating from “inadequate” or “requires improvement” to “good” or “outstanding” between 2018 and 2022, compared with 56% of council-maintained schools.

It found that 81% of LA schools kept their “outstanding” rating compared with 72% of academies that were inspected in their current form and did not inherit grades from their former LA school status.

Nearly three in 10 – 28% – of the same academy cohort saw their outstanding rating fall, compared with 19% of LA schools.

The LGA said it was “good” that the Schools White Paper had indicated councils would be able to set up their own multi-academy trusts (MATs), and the association was urging the Government “to build on this and utilise the knowledge and expertise of councils in supporting schools to improve”.

“By allowing councils to create their own MATs, schools that are currently maintained can continue enjoying the benefits of a strong working relationship with their council in a fully academised school system,” the LGA said.

The Government has said it wants all schools to have joined or be in the process of joining an MAT by 2030.

Anntoinette Bramble, chair of the LGA’s Children and Young People Board, said: “Regardless of whether a school is an academy or council-maintained, what is most important is that children receive the very best education and start in life. This is something we all aspire to achieve.

“While academisation can be a positive choice in some cases, these findings raise questions over whether a one-size-fits-all approach is a guaranteed way of improving results and strengthening a school’s performance.

“Councils continue to demonstrate an excellent track record in improving schools and it is vital Government uses the Queen’s Speech to take full advantage of councils’ expertise and the key role they can play as an effective education partner.

“This is something that should develop at pace, with Government working closely with councils and the LGA to improve the strength and inclusiveness of existing MATs.”

Kevin Courtney, joint general secretary of the NEU teaching union, said the LGA had made an “important intervention on the day of the Queen’s Speech, when the Schools White Paper is set to be centrepiece legislation.”

He added that the research brought into question “the Government’s drive to force all schools to join a multi-academy trust”.

A Department for Education spokesperson said: “The evidence quoted by the Local Government Association fails to take into account many schools will join trusts to address historic underperformance, which can take a number of years, or more than one cycle of Ofsted inspections.

“Our data from over the past decade shows strong academy trusts can transform underperforming schools. More than 7 out of 10 schools which became academies due to underperformance in inspections while they were local authority maintained schools now have a Good or Outstanding Ofsted rating.

“That is why we are opening new routes for schools to join a strong academy trust, including by working with local authorities to allow them to establish trusts for the first time. Schools will benefit from the trust’s support in everything from teacher training to the curriculum, allowing them to focus on what parents and children want and need – great teaching for every child.”