Planning of post-16 provision needs to be restored and inefficient school sixth-forms closed down, MPs who are investigating how to reduce costs have been told.
The Commons public accounts committee heard that the National Audit Office (NAO) had backed claims that small school sixth-forms produced worse results for more money than large sixth-forms or colleges.
But Jonathan Godfrey, principal of Hereford Sixth Form College and a member of the Sixth Form Colleges' Forum, took issue with the NAO's failure to support planned provision.
He said: "I was extremely surprised reading the report that its recommendations weren't a wee bit more bullish about a coherent approach to planning post-16 provision, given that the evidence is so strong. I would say that with sixth-form colleges in particular, if there is a reorganisation planned, that ought to be the first option.
"Local authorities and the Young People's Learning Agency should be seriously steering planners to a more rapid closure of inefficient and ineffective school sixth-forms."
Mr Godfrey said he had researched university drop-out rates in higher education, which were lowest among students from independent schools and sixth-form colleges, followed by state secondaries and general FE colleges.
"It's interesting because the intakes of the secondary schools and the sixth-form colleges are very similar," he said.
The NAO reported that students made more progress at larger institutions, suggesting that they were more likely to succeed when they could choose the course they wanted, which usually meant a large college with a wide range of courses.
Less than 10 per cent of teenagers attend sixth-forms with fewer than 200 students, but these account for 25 per cent of all providers. Below 400 students, the likelihood of sixth-forms adding greater value than expected decreases consistently, auditors found.
"It's certainly our experience that, somewhat counter-intuitively, large providers can be very agile and responsive, and that sometimes large numbers of small providers doesn't necessarily mean more choice," said Maggie Gilliers, principal of Leicester College.
"It is helpful to have some choice, but if that just means a proliferation of very small sixth-forms I don't think that's in the interests either of the learner or the taxpayer."
Declan Jones, principal of Haberdashers' Aske's Federation, said his academies had expanded their sixth-form from 300 to 500 students. He said: "There are benefits of scale. More of our students want to stay because we can offer a wider choice of subjects."
But David Bell, the Department for Education's permanent secretary, said the Government expected that poor or inefficient providers would be weeded out by the market mechanisms of student choice.
He said: "The market has been successful for quite a number of years in the FE system, although it isn't an unfettered market . (But) we need better competitive information between providers, and we need to get advice and information to the users of the market: students, parents and others who have an interest in it."
He said ministers had mechanisms to intervene if providers were underperforming, but added it was not their policy to use them to address the size of providers.
"The Government's policy, and I think it's the right one, is to increase choice and then assume that learners over time will make informed choices," he said.