Two-thirds of those who are pessimistic see closure as inevitable, while the rest feel their future is uncertain.
The Learning and Skills Act which came into effect this week is designed to bring greater co-operation and collaboration among all post-16 education and training providers. But the survey results suggest that exactly the opposite is likely.
Selective and rural schools in well-heeled areas expect to survive. They see themselves as fireproof under the current legislation. But small and urban sixth forms feel threatened by neighbouring colleges and see themselves going under rather than surviving or collaborating.
One headteacher said: "Ministers can hope for what they like but one piece of legislation will not undo years of competition and suspicion overnight."
Local authority chiefs say they are aware of the need for considerable preparation to ensure schools and colleges work in harmony when the Act's key measures come into force next April.
Steven Broomhead, chief executive for Warrington and a former principal and president of the Association for College Management, insists the changes will be beneficial. "But resources must be fully tracked to make sure that nobody falls over the cliff."
The TES survey shows that it is on the question of funding, particularly for the new Curriculum 2000 initiatives, that sixth forms feel most vulnerable.
One school head notes in the survey: "Nothing we have heard convinces us that the new local learning and skills councils will be able to meet the costs in full."
While many of the curriculum and examination costs may have been accounted for, other costs had not - including extra staff costs of up to pound;80,000, she said.
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