A growing movement in which the government pays families who enrol their children in private schools has been traced back to a single major donor at a lone US university.

The idea, known as vouchers ¨C taxpayer-funded subsidies for private-school parents, who are overwhelmingly wealthy ¨C has shot up nationwide over the past year, with seven new states creating voucher programmes and 10 states expanding their existing options.

Advocates describe vouchers as a matter of free choice for parents who already fund public schools through their taxes. Opponents warn that the effect of vouchers is to weaken public schools for the families who need them most, creating a cascading series of harms to local communities, colleges and the overall nation.

The voucher idea has been given an injection of political support since the rise of the Trump administration. But the intellectual underpinnings, according to experts studying the phenomenon, go back two decades, to when the Walton family ¨C the founder and owner of the massive multinational retail corporation Walmart ¨C used its wealth to create a department of education reform at the University of Arkansas in Fayetteville.

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That department inside the Waltons¡¯ home state flagship institution has since produced years of research on data-based rationales that politicians can cite for their pro-voucher policies, as well as graduates who have replicated the strategy elsewhere.

¡°Nearly all of the favourable evidence for school vouchers in particular has a direct tie to that department,¡± said Joshua Cowen, a professor of education policy at Michigan State University. ¡°The empirical evidence for vouchers would be literally non-existent without their influence.¡±

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And the quality of that evidence has consistently proved to be low, said Paul Thomas, a professor of education at Furman University. ¡°Once?,¡± Professor Thomas said, ¡°most of those reports were pretty much discredited ¨C either shoddy methodology or stating conclusions that didn¡¯t match the data.¡±

The work of the Arkansas department was ¡°deeply methodologically flawed¡±, said Bruce Baker, a professor and chair of the department of teaching and learning at the University of Miami.

The Walton family, a longstanding backer of private alternatives to public schools, gave $300 million (?230 million) to the University of Arkansas in 2002, some of which was used in 2005 to create the department of education reform.

The department¡¯s early doctoral graduates included Corey DeAngelis, Martin Lueken, Michael McShane and Ian Kingsbury, all of whom now work at advocacy organisations producing reports used by lawmakers to assert value in the privatisation of US public schools.

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Arkansas officials, asked about the allegations of low-quality research, said in a statement that the department tries to ¡°encourage critical review and debate regarding their findings as well as other related research¡±.

¡°The department¡¯s faculty have a wide range of research interests and expertise, publishing highly cited research and receiving numerous scholarly awards,¡± a university spokesperson said.

Dr McShane and Dr Kingsbury both rejected the suggestion that the department promoted partisanship over precision. Such an accusation was ¡°untethered from reality¡±, said Dr Kingsbury, director of research at Do No Harm, a group that argues against diversity efforts in US healthcare.

¡°I found it to be a rigorous, vibrant, interesting and supportive place to get a PhD,¡± Dr McShane said of his experience at Arkansas. ¡°I¡¯m confident that my record of research and writing speaks for itself,¡± said Dr McShane, now the director of national research at EdChoice, a promoter of alternatives to public schools.

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paul.basken@timeshighereducation.com