Heartsease High School has criticised OFSTED, the state-appointed guardian of correctness, for failing to meet its own standards.
Staff at the comprehensive school were alarmed that their first inspection report contained around 80 errors of spelling, syntax or grammar. Ironically, the inspectors' report, which was otherwise uncritical, identified a need for the school to improve standards of literacy.
But the inspectors' own writing was so lax that, had it appeared in an A-level English paper, the candidate would have been barred from the higher grades, according to deputy head Alan Spoors.
Concerned by slipping standards at OFSTED, he has produced his own report which painstakingly details the areas in which OFSTED "could do better".
His alternative report cites both "embarrassing" mistakes caused by carelessness, and others which, according to Mr Spoors, indicate "real insecurity".
There are 11 spelling mistakes, including using "their" instead of "there", and "too" for "to". In other cases, the OFSTED report defies the dictionary by writing "predominately" and elsewhere uses words such as "posed" instead of "imposed", and "disruptive" instead of "disrupt".
The report is criticised for a "cavalier" approach to the apostrophe, managing to do no better than some market traders with its use of "children's' ".
Mr Spoors said that in some cases the true meaning had to be "prised from sentences" such as: "Teaching standards deteriorate and in Years 9 and 10 where in nearly one third of lessons have teaching which is below average standards. "
The report also received poor marks for grammar, with 14 cases in which a singular noun is coupled to a plural verb.
Mr Spoors decided to to publicise the mistakes after reading a report in a recent TES in which chief inspector of schools Chris Woodhead spoke of OFSTED's "drive to raise standards".
Mr Spoor said: "The experience of this school suggests that there may be some way to go before OFSTED can be regarded as a beacon of excellence. Indeed our inspection report is a worrying reminder that the monitors themselves need careful monitoring."
He added: "This appalling level of literacy does nothing to justify Mr Woodhead's confidence that OFSTED is an organisation fit to lead a crusade for standards. It suggests indeed that if 'excellent and committed' teachers are carrying 'incompetent colleagues' they are not alone."
In a response to the school's complaint about the mistakes, a senior OFSTED official said the errors "clearly do not lend any credibility to the report".
A spokesman for OFSTED acknowledged that the report was substandard and said both the inspector and the contracted team he worked for would remain under scrutiny.