Private schools that make false or misleading claims about their academic prowess have been told that they will be named and shamed.

The Advertising Standards Authority has upheld five complaints about schools in the past six months, including four cases in which private institutions made inflated assertions.

ASA officials have no power to fine schools, but a spokesperson said: “One of the most effective weapons that we have is negative publicity.”

Recent offenders include New College, Cardiff, which has had complaints upheld against it on five occasions since February 2000.

A ruling on March 13 found that the private school’s results were not good enough to support its claims to be “excellent”.

In a regional press advert, New College said it had a “track record of excellent results” and “consistently excellent results”.

But the ASA found that although the school had a consistent record of pass results, “most readers of the advertisement would believe that ‘excellent results’ implied most of the results achieved were graded A, B or C”. It continued: “Because the annual percentage of results graded A, B and C ranged from 88 per cent to as low as 56 per cent, the authority considered that the advertisers had not shown that ‘excellent’ results were consistently achieved.”

New College refused to comment on the case when contacted by The TES. The ASA said it would be talking to the school about the ruling and monitoring its advertising.

In another case this month, King’s School, Rochester, was attacked for calling itself “the top academic school in North Kent”.

The ASA complained that the school had not explained which other schools it considered to be in North Kent and said: “Because they had not shown that they had a better A-level academic achievement than all other schools in North Kent, the advertisers had failed to justify the claim.”

Other recent cases included two schools in West London which made complaints against each other’s advertising. Ealing Tutorial College was rapped for giving an inaccurate average A-level score and misleading information about students who had gone on to study medicine and dentistry.

The Tutorial College of West London also came under fire for referring to itself as a sixth-form college rather than as an independent school. It had also made a misleading claim when it described itself as “top of all sixth-form colleges” because another college had achieved a higher average point score per student.

Private schools were not the only educational establishments criticised by the ASA. A complaint was upheld recently against the London borough of Merton. The borough had claimed in an advertisement that funding to transform high schools into secondary schools would come from the private finance initiative. But the ASA upheld a complaint, saying that Merton had not proved that any of its high schools had accepted the PFI proposals.