The state of Massachusetts has long been hailed as having the best-performing school system in the US.

If it were a country, it would rank sixth in the world for maths attainment, according to the latest Trends in International Mathematics and Science Study (Timss), in which it scored significantly higher than the rest of the US. The state also comfortably outperformed England, which responded by announcing that it would “join high-performers like Massachusetts.in restricting calculator use” in primary schools.

But according to a new report, progress in the pioneering state has “stalled”, with high-performing nations in the Far East “pulling away” from the former trailblazer. Concerns have also been raised that it will be overtaken by other US states unless there is a “fundamental transformation” of its school system.

The damning verdict has been delivered in a report co-written by Sir Michael Barber, a global education reformer who served as head of delivery for Tony Blair when he was prime minister.

Sir Michael has called for Massachusetts schools to be given greater autonomy, in a proposed revamp to the system that critics have compared to the academies programme in England. But the recommendation has been condemned by Pasi Sahlberg, a former policy adviser to the Finnish government.

The research was commissioned by the Massachusetts Business Alliance for Education (MBAE); in a refrain that will resonate on both sides of the Atlantic, the alliance has expressed serious concerns about the number of school-leavers who do not have the skills they need for work.

MBAE chairman Henry C Dinger believes “it has become increasingly clear that the steady progress of education reform over the past two decades has stalled and the chronic achievement gaps between rich and poor have not been closed”.

“Massachusetts is far from the best in the world,” he writes in his foreword to the report. “Some countries are ahead of us and pulling away. Others are catching up with us fast and will soon pass us if we do nothing. Indeed, by some metrics several other US states are improving faster than Massachusetts.”

The report argues that the state risks becoming the next Finland: the ranking of the formerly high-achieving country dropped considerably in the latest Programme for International Student Assessment (Pisa) results.

It also expresses concerns about deep-rooted inequalities in the state. White students are twice as likely as their Hispanic and black peers to become proficient in maths and science, and workers who fail to achieve a high school diploma are six times more likely to be unemployed than the best-qualified workers.

“While the education system in Massachusetts might not be broken, it is certainly not equipped to meet the needs of the 21st century,” the report says. “We believe that for Massachusetts to stand still now would be a major strategic error. Complacency may well be the biggest threat because, under the surface of the undoubtedly positive story, we see some profound challenges facing Massachusetts - and the US as a whole - which need to be surmounted if the promise of the 21st century is to be fulfilled.”

In order to “unleash greatness”, Sir Michael has set out a 20-year programme of reform to establish the state’s school system as the best in the world.

Over the next three years, Massachusetts should focus on implementing new curriculum standards and assessments to meet the needs of employers, he believes, as well as handing “greater freedoms and flexibilities to schools” over hiring staff and extending the school day, in a similar way to England’s academies programme.

“It will take reducing regulation and devolving budgets and responsibilities to the school level, enabling schools to take charge of - and requiring them to be accountable for - their own destiny,” Sir Michael and Mr Dinger told The Boston Globe.

However the proposals have been criticised by several experts, including Dr Sahlberg. In an article written with Boston College academics Andy Hargreaves and Dennis Shirley, he argues that Sir Michael presents an “erroneous diagnosis.based on ideology, not evidence”, portraying a “grim portrait of the state’s shortfalls [that has] little to do with the facts”.

The piece also criticises Sir Michael’s focus on an academy-style approach, pointing out that Massachusetts performed significantly better than England in the latest Pisa results.

“For.policymakers to follow England’s lead in education would be like the [Boston] Red Sox [baseball team] taking coaching tips from the lowly Kansas City Royals,” the article continues. “Most of the solutions proposed in this report are out of line with the world’s best performers.”

Massachusetts’ education commissioner Mitchell Chester also disagreed that the state was stagnating, pointing out that its eighth-graders had the fastest rate of improvement in Timss.

“I do think the bigger point, while Massachusetts has a lot to be proud of and is the top-performing state in the nation, is if we want to remain competitive we need to think about what it will take to build on the strong foundation we have set here,” he said. “There’s no question we need to accelerate our progress to go from good to great.”