US experts have cautioned against Tony Blair’s claims that state-school performance in Florida has improved fastest where pupils are free to go elsewhere.

The British Prime Minister said his trust reforms were designed with Florida’s experience in mind, citing the impact of a scheme in which Florida parents can choose an alternative school if their school has failed in two of the last four years.

In fact that scheme is a voucher scheme, allowing state-school pupils to switch to private schools at the taxpayer’s expense, or to other state schools. It affected only 733 of Florida’s 2.5 million pupils this year and is to be disbanded following a court ruling last month that it unfairly diverted resources from state schools.

The most prominent study on competition and performance is a 2003 report from US conservative think-tank the Manhattan institute. It found that schools facing competition or the threat of it, as a result of Florida’s reforms, showed a 6.7 to 10.1 per cent improvement in state test scores relative to schools with no competition.

Top US academics did not dispute the findings, but the conclusion the report draws that “schools improve when... forced to compete in the market”

were “highly challenged” in research circles, according to Henry Levin, professor of economics and education at Columbia university’s teachers’

college.

Under the A+ Program, introduced in 1998, Florida’s schools are graded from A to F for “failing”, based on test scores and other criteria. If students leave when schools fail twice in four years, the school forfeits funding under a per-pupil formula.

But a Florida university economist, David Figlio, who has conducted extensive research on Florida’s reforms, said it was debatable how far competition has been the driving force behind “incontrovertible improvement in student performance”.

Rigorous academic accountability deserved the “lion’s share” of credit, he said. This included the stamping out of “gaming” - where schools concentrate on easy-to-affect variables, like test scores in easier subjects, to improve their standing - and the impact of naming and shaming “failing” schools. This motivates schools to turn around poor results, he said. Failing schools also receive cash infusions and staff development.

Marcus Winters, co-author of the Manhattan institute report, countered that they sought to “control” for any stigma by tracking schools that failed only once in four years, finding that after the threat of competition was lifted their performance “regressed”.

In addition to the voucher scheme, under US-wide reforms not mentioned by Mr Blair, pupils can transfer to other state schools if the school missed progress benchmarks two years running, but only 6,762 pupils out of 450,000 at such schools did so last year.

America’s more-than 3,600 publicly-funded, but independently-run “charter”

schools offer a more analogous reference point, said Mr Figlio. But here too, evidence of any benefits from the competition they pose state schools is not clear-cut.

Duke university economist Helen Ladd said she found no positive impact on schools near North Carolina’s 97 charters.

But she also tracked students transferring to the North Carolina charters and found their test scores actually declined over five years.