The proportion of teenagers scoring at least five Cs at GCSE including English and maths has fallen for the first time, official figures have shown.
In total, 58.6% of pupils in England achieved five A*-C grades, including the two key subjects, down almost half a percent on 2011, according to Government data.
Statisticians said the drop was down to fewer English entries from private schools, but there are also likely to be concerns that issues with this year's GCSE English grading may have played a part.
The figures show that one in four pupils were entered for all the subjects in the Government's English Baccalaureate, with 18.1% achieving the EBacc.
This is up on last year, when 23.8% entered and 17.6% achieved it. Teenagers are awarded the EBacc if they score a C grade or higher in English, maths, science, history or geography, and a language.
It is the first time that the number of pupils scoring five A*-C grades including English and maths has fallen since 2004/05, when the Government changed the way it collects the figures. Government officials said the fall was down to fewer private school pupils being entered for GCSE English.
There has been an increase in overseas students attending UK fee-paying schools, and many of these either do not take English, or take English as a second language, which is a different subject, they said.
The statistics, published by the Department for Education, show that the numbers of teenagers achieving this benchmark has risen by 0.1 percentage points in state schools alone. In total, 58.3% of state school pupils achieved at least five Cs, including English and maths. More than four in five pupils (82.5%) from all schools in England gained five or more GCSEs at grades A*-C in any subjects, up two percentage points on 2011.
Verity O'Keefe, employment and skills adviser at EEF, the manufacturers' organisation, said: "Today's drop in the number of young people achieving five good GCSE passes, including English and maths, shows that we are still some way off the mark the economy needs to grow the pipeline of people with good basic skills.
"Many employers use similar benchmarks when recruiting young people, with three-quarters of manufacturers prioritising attainment in maths, English and the sciences when recruiting apprentices. However, a lack of attainment in key subjects is still restricting firms' ability to fill vacancies and Government must now set a target of 65% of students achieving five good passes which includes English and maths."