It’s been just over two years since the government announced plans for sweeping new powers to take over local authority schools and set us on a course for full academisation by 2020. By now, we were expecting schools to be being converted en-masse in poorly performing local authorities or in those areas where the majority had already converted.

But, of course, the legislation required to deliver it never happened. The vote to leave the European Union brought to an end the political careers of the prime minister and his chancellor - who had announced the policy in what was to be his final Budget. Their departures were swiftly followed by that of education secretary Nicky Morgan, returning to the backbenches clutching a copy of her recently published White Paper, Educational Excellence Everywhere, with some of its more controversial elements soon to be a footnote in Department for Education history.

Two years on, while academisation has continued and has even accelerated, we remain in a mixed system. Today, the Education Policy Institute has published its latest analysis of the performance of academy chains and local authorities. This isn’t about pitting local authority schools against academies and debating which is best - our previous research has shown there’s not actually much difference - it is about identifying whether the system we have inherited, by default, is working.

In many ways yes. But, to put it bluntly, some school groups are simply not good enough and are failing their pupils. We find examples of both local authorities and academy chains that are underperforming. The difference between the highest and lowest performers is equivalent to about a term’s progress at the end of primary, or half a grade in every GCSE subject at the end of secondary.

Some of the academy groups that appear near the bottom of our tables will be familiar to anyone with a passing interest in the school system. Bright Tribe, Wakefield City Academies Trust and the Education Fellowship Trust have been high-profile cases of failure. But is it system failure?

Strength or weakness?

Proponents of academisation will highlight that the option to close down poorly performing trusts and move schools to new providers is one of the features, and indeed one of the strengths, of the academy system.

There is some merit in that argument. Consider the fact that there are local authorities in which performance has been consistently low, and may remain so. Parents of primary-aged pupils in Kirklees, Dorset, Walsall, Rutland and Poole, and of secondary-aged pupils in Newcastle-upon-Tyne and Wolverhampton, do not have the option of some other high-performing local authority coming in to take over their schools.

But where the argument falls down is that the process of moving schools on - known as “rebrokerage” - can be slow. In some cases, it has taken over a year from the announcement that a school is to move to it joining its new trust.

Such delays and uncertainty are likely to have knock-on implications for teacher recruitment and retention - often in schools that are most in need of high-quality teachers - and on admissions, with implications for funding.

But while there is a need to move swiftly, regional schools commissioners (RSCs) are also having to ensure that schools are not simply bounced between underperforming trusts. The delays seen so far are not necessarily an indication of failure and may instead reflect that schools are being moved to appropriate trusts.

Act now in at-risk schools

What is needed is for the capacity to be in place before we reach a point where a trust collapses and schools are left in limbo. Performance data such as that published in our report today provides some insight into those trusts that are most at risk.

In order to make decisions that work best for individual schools, the RSCs also need a range of options available to them. That’s why we argue that it may be appropriate for schools to return to local authority oversight in the same way that a school may be moved to a high-performing academy chain. This would provide additional capacity within the system and would go some way to reducing the time taken for rebrokerage.

Overall, the public debate needs to move on from academies versus local authority schools and recognise that there are strengths and weaknesses in both. Now that the pressure to academise all schools is off, the government should focus its efforts on building school capacity in areas where the system is currently letting children down.

Jon Andrews is deputy head of research and director of school systems and performance at the Education Policy Institute