As sixth-form colleges jockey for position with schools towards the top of the exam tables, some are said to be resorting to selection by ability to ensure they enrol only the brightest applicants who will achieve the highest exam passes.

Other tactics are said to include preventing less promising candidates from sitting A-levels to avoid bringing down a college’s average points score, or channelling weaker students towards subjects they are more likely to succeed in. Some colleges entering a high number of candidates for general studies are accused of trying to raise overall scores through “easy” passes.

The devices, which are said to be on the increase, closely resemble those alleged to operate in schools - the main competitors of sixth-form colleges.

Colleges which already rank high in the tables fear the system of measuring performance through exam success will encourage the tactics to spread.

Mike Galloway, principal of York Sixth Form College, which came second from top in this year’s FE college performance tables, said: “If the league tables take on a credibility with the public that is out of proportion to what they are actually telling us, some colleges may be tempted to adopt these policies. I think that would be deeply regrettable and not in the interests of the young people we are trying to serve.”

He predicted competitive pressures of the FE market-place would ultimately prompt some colleges to succumb, even if they had not already done so.

At Aquinas College, Stockport - eighth in the college tables - principal Dr Ambrose Smith shares Mr Galloway’s anxieties over the effects of ranking by exam performance. “If you are not careful you can get pushed into doing things which are not in the best educational interests of the students. I have told staff our placing is to their credit, but our key aim stated in our prospectus is the care of our students.”

Aquinas, though over-subscribed, selects purely on a first-come, first-served basis, he added. Some students beginning A-level courses have only four Cs at GCSE.

Most college principals are convinced students and their parents take little or no account of league tables when choosing a post-16 destination. In areas of highest achievement and stiff competition, however, there is a marked increase in concern over the performance tables. One principal contacted for comment by The TES on the day of the tables’ publication immediately asked for details of the relative placing of a rival college.

Philip Eyles, principal of King Edward VI College, Stourbridge, ranked third in the country, acknowledged tables kept colleges “on their toes”. His college’s ability to attract students rested on exam results. But he highlighted the increasing trend in some schools and colleges for entering high numbers of students for general studies examinations to boost average scores.

Even at the very top of the table, the current system of assessing performance has come in for strong criticism for penalising colleges while favouring private schools. Colin Greenhalgh, principal of Hills Road Sixth Form College, Cambridge, where students are selected on a catchment area basis, criticised the tables for reflecting an outdated image of an A-level-taking “educational elite”.

Pressure to expand in order to help meet national training targets had seen Hills Road grow by 60 per cent in three years, causing an inevitable lowering of its average exam score, while public and independent schools were permitted to keep numbers steady, he said.

“If you take our 200 top-performing students they are way up there with Winchester and Westminster, but because we take more students we get penalised. I get increasingly concerned that the public might get the impression that you have to go to a grammar or an independent school to get top quality results. ”

Along with general further education colleges lower down the performance league, the high-flying sixth-form colleges want greater recognition of vocational qualifications and, crucially, for a value-added element in the tables.