TONY Blair's controversial city academies represent a "high-risk" investment for wealthy donors who want to support education, says a report today.
There was not enough evidence to say whether the privately-sponsored schools were the best way for donors to spend their money, the study found.
But mixed Ofsted reports and exam results did raise serious doubts over the "cost-effectiveness" of the scheme.
The report from think-tank New Philanthropy Capital (NPC) concluded: "Academies are a risky investment: they can and do fail."
The study is the latest blow to the Prime Minister's flagship policy for transforming state education in England's inner cities.
It follows the damaging "cash for honours" row over claims business figures were told they could get knighthoods or peerages.