Recent policy changes signal a rise in new school sixth forms even though they may damage the quality of local 16-19 education.
This follows the Government's decision to give academies and specialist schools minimum scrutiny when it assesses their proposals to set up new sixth forms.
The Learning and Skills Council recently set out a new and transparent process for agreeing changes to education and training at 16-19. Under this, there will be "competitions" to determine the best and most cost-effective way of meeting need.
Where there is a need for new provision, any institution - school, college or private provider - can submit proposals. These proposals will then be considered against transparent criteria. A key test will be to demonstrate how the proposal meets an independently determined measure of need.
In other words, the proposal must be demand-led, not driven simply by institutional ambitions.
Such a system makes obvious good sense. So, it is worrying that some proposals - specifically those from academies and specialist 11-16 schools - will be fast-tracked to a decision without such careful scrutiny.
Indeed, the Department for Education and Skills' strategy says there will be "a presumption" that such applications will be agreed.
Such exceptions could damage local planning and undermine confidence in planning as a whole, particularly since proposals emanating from these excepted routes are the ones that threaten the quality of provision most.
There are four reasons for this. First, the number of young people in the 16-19 age group is set to fall, not rise. Significant shortages of places in an area are therefore likely to be rare.
Second, there is little evidence of a shortage of level 3 (A-level equivalent) places; the priority is more and better opportunities at level 2 (GCSE-equivalent) and below. Yet proposals from 11-16 schools and academies are likely to focus on level 3, as indeed does the consultation document.
So, careful scrutiny of proposals, it seems, will not apply in precisely those cases where there is most danger of them being driven by institutional ambitions, not learner need.
Third, the creation of new level 3 places in an area where demand is relatively static will not only threaten the financial viability of existing providers but limit the choice of subjects.
Research shows that the range of subjects offered at level 3 varies directly with size of cohort. Unwarranted expansion of the number of providers in an area will lead to minority subjects being axed from the timetable.
Fourth, in some areas there are few school sixth forms because of a deliberate local authority policy to use sixth-form colleges.
To introduce a new sixth form in such an area could be very destabilising and threaten quality. Many schools feel, rightly or wrongly that having a sixth form gives them a "competitive edge". It will be hard therefore to resist a "domino effect" as each school tries to set one up to protect its recruitment.
It is important that decisions to reshape provision focus clearly on the need to maintain and improve quality. Contrary to much received wisdom what we know is:
* Tertiary colleges which, by design, face the least competition at 16-19 are disproportionately represented among beacon colleges, which are the best performers. Also, very large FE colleges on average get better inspection reports than others.
* There is no statistical relationship between the degree of specialisation of FE colleges and their quality; and a Learning and Skills Development Agency study of specialist colleges found that they offered no consistent differences in quality that justified their 10 per cent additional cost.
* There are no special advantages offered by sixth-form centres, compared with FE colleges without such centres; and an LSDA study on mixed-age learning in colleges found strong support for it from learners and teachers.
* School sixth forms perform no better than FE colleges once the prior attainment of pupils and selection is taken into account.
* There is no evidence to show that increasing the number of school sixth forms in an area will increase participation.
Recent research carried out by the National Foundation for Educational Research for LSDA suggests that, far from being proven, the opposite might be the case.
Finally, it is good that cost-effectiveness will be a criterion for determining who wins the competitions - along with quality it should be central to all decisions to expand post-16 provision.
Because of the 14 per cent funding gap between schools and colleges, this gives renewed urgency to calls for a common funding approach.
Mick Fletcher is a research manager at the Learning and Skills Development Agency.