More than half the schools in England are facing cuts to their budgets, a survey of heads and deputies suggests.
The research comes as the Department for Education announced that more than 1,000 schools have applied to become academies since June 2010.
Education Secretary Michael Gove said: "A third of secondary schools are now either an academy or have started on the road to conversion. This represents a fundamental shift in power away from government and towards teachers.
"Teachers, not politicians or bureaucrats, know best how to run schools."