Rising numbers of secondary schools are seeking academy status in the belief that it will help them financially in a time of spending cuts.
Almost half of England's secondaries are intending to convert, or have already converted, according to a poll by the Association of School and College Leaders (ASCL).
Of these, nearly three-quarters (72.3%) believe their school will benefit financially, while nearly three-fifths (58%) believe it will bring greater freedom and autonomy.
As academies receive their funding directly, these schools have been able to protect their budgets when others, who are given their money from local authorities, have not, ASCL said.
Of the 1,471 ASCL members questioned, 8% said their schools have already become academies, while 38% said they were in the process of converting or intend to, as soon as they are eligible.
Some 34% said they were undecided, while just under a fifth (19%) said they have no plans to become an academy.
ASCL general secretary Brian Lightman said the numbers choosing to convert have risen since the union conducted a similar survey last autumn.
"The Department for Education has said in its documentation that there should be no financial incentive or disincentive for becoming an academy but this is certainly not the message that is getting to schools," Mr Lightman said.
"It is very clear that early converters have gained financially and therefore will be able to protect their budgets in ways which other schools have not. Although they know that this funding bonus will not be sustainable, they see it as a way of cushioning their schools from the cuts of the next few years.
"In many areas local authority services have been decimated leaving schools with little reason not to convert."
