Ofsted's plans to bring school inspections in line with those of colleges have been delayed due to the Department for Education's concerns about the accuracy of its own official data.
In response to colleges' long-standing claims that they are judged more harshly than schools, the watchdog has vowed to level the playing field in its new frameworks, which come into effect next month.
But just weeks before what the Sixth Form Colleges' Forum (SFCF) had hailed as a "game-changing" move, one of the key changes - allowing inspectors to assess schools' success rates for the first time, as they do with colleges - has been put on hold.
TES understands that the DfE has told Ofsted that, while colleges' success rate data has been tested for a number of years, the data for schools is not yet accurate enough. The success rates, which reveal the proportion of students who complete their courses, are not expected to be in official use for schools until next March, six months behind schedule.
College leaders have hit out at the "disappointing" news, warning that the failure to assess colleges' performance in relation to other local providers could lead to harsher verdicts for those who are inspected in the first few months of the new framework.
"It's disappointing that it's going to be six months late, especially when Ofsted is ratcheting up the pressure on schools and colleges," said Julian Gravatt, assistant chief executive of the Association of Colleges. "The risk is that a college's results may not look to be as good as surrounding schools, but it is very plausible that it could actually be performing better."
David Igoe, chief executive of the SFCF, said the situation was unfair on colleges. "There are no natural data sets that are reliable that look at the performance of all providers," he said.
Mr Igoe added that he had been given assurances by Ofsted that colleges would not lose out as a result of the delayed changes. "There will be a clear statement to inspectors that they must take the context of the college into consideration; how it performs in relation to the performance in the patch. We will be vigilant," he said.
He called on inspectors to refer to schools' provisional success rates for guidance, adding: "They can look at it, but they can't use it (in their inspection reports)."
An Ofsted spokeswoman said that in the absence of comparable data for schools and colleges, it would publish "guidance that will advise inspectors . on the use of the full range of achievement measures currently available to them".
"We look forward to receiving data from the Department for Education so that inspectors can judge schools and colleges in a similar way," she added.
In the meantime, FE and sixth-form colleges will only be judged against the average success rates for colleges, with no direct comparison available with local schools.
Concerns were also raised last year by the Education Select Committee, which reported that "processes for sixth-forms, schools and colleges are not consistent with each other".
This is a major cause for concern at Lancaster and Morecambe College, which, according to principal David Wood, is facing increasing competition for students from neighbouring academies that are opening their own sixth forms. "It's disappointing that we haven't got a level playing field of data and information for people to make a judgement call on," he said. "The sooner that happens, the better."
A spokeswoman for the DfE said that school success rate data should be "available, comparable and robust by March 2013".
"Until then, the statistics should be used as the basis for a discussion with headteachers rather than a guaranteed measure, and inspectors will be encouraged to do so from September," she added.
What the government said:
"We are committed to establishing common performance measures for 16-19 education and training. We will work with the Department for Business, Innovation and Skills to look at ways of publishing data in a more transparent way to allow parents and students to compare school sixth forms with all other post-16 providers."
From White Paper The Importance of Teaching, November 2010.
Original headline: Plans to level playing field between schools and colleges delayed