Fewer than a quarter of 16-year-olds achieve five good GCSEs that include the “core academic subjects” of English, maths, science and a foreign language, according to figures published by the Conservatives on Monday.

The data show an almost unbroken decline in the proportion for several years, reopening the debate over whether teenagers are learning the right subjects, in spite of ever improving GCSE grades, likely to continue when this year’s results appear on Thursday.