No slang allowed, innit?
Even the high-achieving pupils made "almost unforgivable" basic errors, said the Edexcel examiners in findings that will add to pressure on ministers to raise standards.
In its annual report on English GCSE, Edexcel said: "There were... surprising numbers of lapses in standard English, particularly in verb forms; 'gonna', 'aint', 'wanna' and 'shouda' appeared with surprising regularity.
"Candidates...should not use street language and text style."
English GCSE is not the only exam in which pupils' shortcomings have been held up for scrutiny by underwhelmed professionals.
In its report on a French exam taken by GCSE students aiming for top grades, examiners offered a withering comment on some candidates' inability to spell the name of their subject.
"It was disappointing to see the number of candidates who could not spell the word Francais accurately even though it was printed in bold directly above the space for candidates' answers," they said.
For A-level English literature, examiners were generally much happier and repeatedly praised pupils. But they did express concerns about the inability of some sixth-formers to spell the name Shakespeare in a paper entitled "Shakespeare in context".
In that respect, candidates had something in common with the Bard, whose family records are said to show 44 spellings of the name Shakespeare. Even William spelled it two ways in his will: "Shakspere" and "Shakspeare".