that a significant number of colleges were considering taking on pre-16 students to help ease their financial burdens.
Since September 2013 the government has allowed colleges to enrol younger students, who attract extra cash from the Education Funding Agency. Although several further education colleges have started to accept younger students, so far only two of England's 93 sixth-form colleges have done so in large numbers.
But more principals are beginning to consider the possibility as the sector faces serious pressures, including demographic changes, competition from school sixth forms and new 14-19 providers, and the so-called "learning tax", which prevents sixth-form colleges from claiming back VAT on purchases.
However, Mr Igoe warned against the idea. "What looks eminently sensible and coherent on paper can often mask significant practical difficulties," he told delegates at the Westminster Education Forum event in London last week. He said that key stage 4 required different approaches to teaching and support, and cautioned that some teachers would need significant retraining to work with younger pupils.
Other issues included younger students' personal development and behaviour, he said, as well as the need for new procedures to address safeguarding concerns.
Mr Igoe said that although entering the 14-16 market could help colleges to maintain funding levels and reduce the need for staff redundancies, there was very little "real appetite" for it. "It will be driven by economic imperatives rather than any conviction about the educational coherence or otherwise," he added.
"Sixth-form colleges have built their reputation around their specialism of delivering high-quality qualifications to 16- to 19-year-olds. They would be wise to stick to that knitting before finding a whole new thread to weave and master."
Mark Bramwell, associate director for sixth-form colleges at the Association of Colleges, said that some principals were giving "serious" consideration to the move, but added: "We are not recommending any particular pathway.
"We know the funding situation is not going to get any better, so it's right that colleges should be looking strategically at all the options."
Mr Bramwell said colleges should take into account a number of concerns around enrolling younger students. "It may change the character and ethos of the college and it could put them at risk of undoing the good relationships with their local secondary schools, upon which they are reliant," he added.
John Ruskin College in Croydon, South London, is currently the only sixth-form college to have dedicated provision for key stage 4. It made the move in 2012 at the request of the local council, in order to meet a need for extra places. The college currently has 137 students who have their own area of the building and wear uniform.
Philippa Levy, the college's director of learning with responsibility for key stage 4, said the provision was planned well in advance to meet the needs of a pre-16 cohort, including specialist training for staff and a review of all college policies.
She said that, in order to make it viable, provision should be based on need and not economic decisions. "I would be very surprised to see colleges moving into this area to increase their income," she added.
"You need a significant number of specialist teaching and support staff to make it work, which means a financial outlay before you start. It's a positive step to meet local needs, but in terms of financial rewards, it's limited."
`The demands are different'
In September 2011, Wilberforce College in Hull became the first sixth-form college in England to accept students aged 14 and 15, after the closure of local secondary David Lister School.
With funding from the local council, Wilberforce enrolled 56 pupils who were housed in their own purpose-built section of the college and continued to wear uniform.
Colin Peaks, an assistant principal at Wilberforce College, says it was a unique situation: "The students came as a group who knew each other, which made it easier for them. They were some of our most successful students."
More than 70 per cent gained five A*-C GCSEs and almost 90 per cent continued their studies at the college after key stage 4. However, Mr Peaks says Wilberforce decided not to make it a permanent arrangement because it did not want to compete with local secondary schools and jeopardise good relations.
Although the move was a success for Wilberforce, Mr Peaks would advise other colleges to think carefully before taking on younger students. "The demands are different; there are issues around teaching, behaviour, pastoral care and support. It could be potentially difficult without the right staff," he says.