Pupils can gain top grades at GCSE English despite having poor spelling, a leading public school claims.
Sir Winston Churchill is among Harrow's former pupils
Harrow School, in west London, which sets its own literacy test, found some teenagers with A* grades had a "tenuous grip" on some aspects of language use.
English teacher Tom Wickson said staff had become "increasingly concerned" at standards expected of GCSE students.
Employers would be unimpressed if job applicants could not compose a formal letter, he added.
'Can't be right'
Writing in the school magazine, Mr Wickson said: "Can't spell simple words and can't punctuate a simple sentence, but can still get an A grade in GCSE English? That can't be right, can it?
"Well, yes, at Harrow we frequently find that can be the case."
The test, which has been set for sixth-formers for the last two years, covers grammar, spelling and punctuation.
Those who fail - usually about 20 out of 160 students at the first attempt - receive extra lessons until they pass.
Mr Wickson said: "Simple technical accuracy is not prized as highly as it once was.
"You can get a good grade in GCSE English by getting the correct answer - and whether or not it is presented very formally is of lesser importance."
He added: "In response to this uncomfortable situation, we have put even more emphasis on teaching boys the importance of spelling and grammar when they first join the school.
"This is beginning to alleviate the problem. But we are still aware of the need to take stronger remedial steps to help some of our pupils who have moved into the sixth form yet continue to have a tenuous grip on some basics of English."
The Qualifications and Curriculum Authority, which oversees exams in England, has published a list of skills candidates should demonstrate to gain a grade C in GCSE English.
The proposals, which are up for consultation, include a requirement to punctuate accurately using commas and apostrophes.
The QCA is looking at two approaches: one using free-standing grammar tests, the other incorporating them into the GCSE exams.
Assessors at the AQA exam board noted many weaknesses in last summer's English papers.
In a report they said: "In some answers, the full stop had almost entirely disappeared, and capital letters were also virtually non-existent."
But a QCA spokesman said: "The current system of GCSE examinations is designed so that pupils are able to demonstrate their ability and competence in a wide range of skills.
"There is a need to ensure that young people are fully equipped with the functional skills that will enable them to engage purposefully as citizens and in employment, and we are currently working with several other organisations to develop this new set of qualifications."
Last summer, 71.2% of GCSE English candidates gained grades A* to C.