English examiner Anne Barnes said rising pass rates at GCSE did not necessarily mean standards in education were improving.
Mrs Barnes said she had seen exam papers where pupils used "soap opera language" in essays.
One case had a whole answer written in the style of a mobile phone text message.
The comments come as thousands of teenagers - and parents - across England, Wales and Northern Ireland await their GCSE results next Thursday.
Last year the number of pupils achieving grades A* to C rose by a half of one point to 57.1% and ministers and teachers will be hoping to see another rise this year.
'Exam-orientated'
Mrs Barnes said she feared exams had become more important to everybody over recent years.
"It doesn't mean to say standards of writing and education have got better," she said.
"People are more exam-orientated - exams are important rather than education.
"I don't myself regard this as a positive development. It has serious dangers and disadvantages."
'Rigorous system'
The Department for Education said it did not accept Mrs Barnes's concerns.
"We make no apologies for a rigorous system of assessment and testing because it benefits children of all abilities," a spokesman said.
"Of course we want to ensure that there's creativity in the curriculum. That's why we've placed such emphasis on music, sport and the arts.
"But it is important that we get that balance right," he said.
John Dunford, general secretary of the Secondary Heads Association said there was "no question" that standards had improved.
Schools now worked more closely with exam boards and had much more information about how tests were set and marked, Mr Dunford said.
"This enables teachers to focus better on the requirements of exam papers and that will inevitably improve the results of young people."