Colleges, which claim enormous success with the academic "gold standard" and vocational courses, are hoping to step up pressure on the new Government for a coherent policy for full-time 16 to 19 education - and an end to disparities between colleges and school sixth forms.
Principals warn that some sixth-form colleges could close if the current funding squeeze continues - and are pressing for a level playing field with school sixth forms, which currently get about 30 per cent more cash per student, while retaining the freedom to expand.
They insist that their general argument holds for full-time 16-19 education throughout FE, but they emphasise what they see as huge benefits in their role as specialist providers for young people between school and higher education or work.
Sixth-form principals, at the heart of the politically explosive debate over A-level standards, could cause problems for the new Government.
Conservative ministers backed the A-level "gold standard", but have left sixth-form colleges, which include some of the highest flyers in the A-level leagues, underfunded.
Principals argue that ministers have promoted school sixth forms without regard to the cost or the possible effect on colleges. They also complain that there has not been a proper debate about the future of full-time 16 to 19 education.
John Guy, principal of The Sixth Form College, Farnborough, Hampshire, led the onslaught, arguing that many sixth forms were facing 20 per cent cuts under the Further Education Funding Council's three-year plan.
Farnboroug h, which faces a cut of #163;100,000 this year and a student numbers freeze, was confirmed as one of Britain's top three colleges by inspectors last week.
Another college, Colchester sixth form, also joined the top three, with students' work described by inspectors this week as "outstanding".
Principal Ian MacNaughton said: "We are hoping that the quality of the experience and the value for money that sixth-form colleges provide will be recognised. The standard of achievement both in academic and vocational courses, is extremely high.
"They are specialist institutions catering for the specialist needs of 16 to 19-year-olds, giving them a halfway house between school and the world of higher education or work."
Nick Brown, principal of Oldham Sixth Form College, warned sixth-form colleges could close under the current funding regime. "I'm hoping the Association of Colleges will be extremely forceful on this," he said. "The country is in danger of losing one of its greatest assets. There is no policy on 16 to 19 education - if there was we could address the national shortages in science, maths and languages."
Farnborough has expanded into general national vocational qualifications at all three levels, but has retained a campus atmosphere and strong pastoral care - which Dr Guy says sets his college apart from the general tertiary institution a mile away, and provides the basis for its academic success.
Dr Guy, who represents sixth forms on the Association of Colleges, warned that cuts to FE colleges would hit high-cost A-level courses hard, and could mean a move to far greater selection.
He said: "I think that's a possibility and it's one that we would not welcome because we believe we can provide a good education for the very bright and those who have more difficulties - something which is shown by our results."
He said the FEFC's move to equal funding for all colleges would mean 20 per cent cuts in three years for many sixth-form colleges. "How can a college accept that sort of cut on top of the savings they have already made?" he said.
"Cutting out 20 per cent of costs at a sixth-form college without affecting quality is not possible. We have an average class size of 17.3. School sixth forms are funded for classes of about eight. They are the same youngsters and I think that the opportunities available in a place like this are so much greater.
"We like to think people come here and broaden their experience. For the most part youngsters who stay at school have a narrowed experience because some students leave. We are finding that youngsters are applying to us even if their school has a sixth form."
The college certainly exerts a pull on applicants - 20 per cent of its intake are teenagers who have rejoined the state system from independent schools.
Dr Guy said: "The notion that 11 to 18 education is what students want has to be questioned - as has the assertion that it is what parents want.
"In terms of spending public money, I do not know how they can justify the opening of loads of small school sixth forms."
Under current funding policies, Dr Guy sees no chance of new sixth-form colleges opening even though the sector has been successful.
"More than a third of students between 16 and 19 are in sixth-form colleges, so we are a very significant and important part of the education system."
Dr Guy's funding worries are not restricted to sixth-form colleges, but relate to all FE institutions.
"The FEFC's concern about the effects of cuts on 'first chance' 16-to 19-year-olds is beginning to be felt, and I think ministers are aware of that.
"There have been questions raised about priorities in funding and I think the sector is mature enough to make these sorts of decisions. That's what I would like the FEFC to do now.
"A lot of the high-quality provision in the sector has been identified as going on in the sixth-form colleges. They are in some ways leading the sector. Sixth-form colleges are a jewel in the crown."