Secondary schools have turned their backs on traditional academic subjects in favour of other options, new league tables suggests.
They show that low numbers of pupils in many of England's secondaries are achieving the Government's flagship new "English Baccalaureate".
The measure, included for the first time this year, shows how many pupils are gaining at least a C grade in English, maths, science, either history or geography, and a language.
An analysis of the tables suggests that at more than 3,000 schools less than half of teenagers reached the "English Bacc" benchmark. More than 300,000 children in total are taught at these schools.
The low numbers suggest that schools have been turning to other qualifications, such as vocational courses, which are often seen as "softer" options, rather than stick to traditional subjects.
It has previously been suggested that around one in six pupils nationally will achieve the "English Bacc" threshold.
Education Secretary Michael Gove announced the introduction of the English Baccalaureate after saying last year he was "worried" by the decline in the number of students taking GCSE sciences and languages under the current system.
But headteachers have expressed fury that the measure has been included in this year's tables, just two months after it was officially confirmed.
They have said it is "unfair" on schools to bring the measure in so quickly.
A league table of the top 200 schools in terms of the Baccalaureate puts Bishop Wordsworth's Grammar School in Salisbury top, with 98% of pupils achieving the measure.
Headmaster Stuart Smallwood said the school, which caters for boys aged 11-18, has always had a "traditional academic curriculum".
He said he was in favour of "the traditional approach" and that it was "probably right" that Mr Gove has introduced the Baccalaureate.
But he acknowledged there had been some "disquiet" amongst some headteachers about its introduction, which he said may not have been done in the best way.
"It's a bit like asking you to take an exam syllabus and then saying the exam's changed.
"To be fair, schools should probably have been given warning so that they could, if they wanted, make any adjustments to their curriculum."
He said that giving pupils a broad curriculum up to GCSE allows the school to see how they are doing, and allows pupils to keep their options open.
At Dartford Grammar School, some 97% of boys attained the "English Bacc" measure.
Headmaster John Oakes said: "At Dartford Grammar School we are convinced that the English Baccalaureate at GCSE prepares students extremely well for the broad and balanced demands of the prestigious International Baccalaureate Diploma programme in the sixth form, an excellent route to future success at university and beyond.
"We are pleased that the new English Baccalaureate benchmark recognises the importance of languages - the most under-valued area of the English curriculum."
But Ian Johnson, principal at Marlowe Academy, which came third from bottom in terms of percentage of pupils achieving five Cs at GCSE including English and maths, raised concerns.
"In the current year about 10% have a chance to get the English Baccalaureate. We can't change what the students are studying in the middle of the year," he said.
"We are making changes for students due to begin GCSE studies in September.
"I think the focus on English, Maths and Science is right, but why humanities has to be History or Geography is a mystery.
"Whether the English Baccalaureate is right for students of all types is questionable.
"I think for some students it's an appropriate curriculum, but for others it isn't."
Brian Lightman, general secretary of the Association of School and College Leaders (ASCL) previously told BBC online that the "English Bacc" was a "retrospective indicator".
"It's an indicator over which schools have no control as it was not in place when the children concerned studied for their exams," he said.
"This is going to disadvantage schools in poorer areas. This is a very academic qualification."
A further analysis of the figures suggests that, at around 2,500 secondaries, fewer than a quarter (25%) of pupils are achieving the English Bacc. This figure includes private schools.
This suggests that estimates that 15% of teenagers nationally will meet the benchmark are on target.
Around 3,950 schools are included in today's tables, excluding those that are closed.
The majority of schools listed in the tables are state schools.