Manchester Grammar School is the fourth independent school to move over entirely to the International GCSE, and increasingly private schools are offering the qualification in at least one subject.
From September Manchester Grammar will switch over to the IGCSE
Manchester Grammar School is already offering IGCSEs in maths, biology, chemistry and physics, and will offer it in seven more subjects from September.
It says the IGCSE is simply a more rigorous assessment.
It is based predominantly on final exams, and the school says this provides more of a challenge to the brightest students.
From this September the ordinary GCSE will be reformed, with the element of coursework largely replaced by "controlled assessments" done under supervised conditions within schools.
And it will become more modular, allowing pupils to re-sit certain parts to improve their marks.
The headmaster of Manchester Grammar School, Dr Christopher Ray, says the impending changes convinced him to move away from GCSEs completely.
"Controlled assessments are cumbersome and time-consuming and restrict the ability of schools like MGS to provide inspirational teaching for the most able pupils," he said.
He said he thought the changes "might bring some benefits to average or lower-ability pupils".
Is the IGCSE a harder qualification?
The answer to this perhaps depends on whether you regard exams as harder than coursework or modular qualifications.
Manchester Grammar said the proportion of students gaining A grades in their Year 11 exams had risen since the IGCSE was introduced.
In 2006 the Qualifications and Curriculum Authority, which assesses the strength of various qualifications, said the IGCSE was "not suitable for assessing what pupils in England learn".
It said the IGCSE did not meet the subject criteria because of the "major differences" between it and the GCSE.
The IGCSE is more 'linear' - based mainly on final exams
For example, the QCA noted that there was significantly less prescribed reading for English in the IGCSE, no speaking test for French, and no non-calculator exam in maths.
It said the ordinary GCSE was more closely bound to the programme of 11-16 learning and so could be said to assess this better.
Does the IGCSE place more emphasis on international affairs?
The IGCSE essentially has to be more flexible, because it is available in more than 100 countries. It does not have to adhere to the English national curriculum.
It might well be taken by a pupil at an English school in a foreign country.
It does not include the compulsory study of Shakespeare, for instance, though his works would still be an option in an IGCSE.
How popular is the IGCSE?
Numerous independent schools have moved towards IGCSEs in recent years, though only four now offer them exclusively.
In 2008 there were 40,000 IGCSE exam entries, according to the Independent Schools Council (ISC), which represents most of the bigger institutions - a leap from 15,000 in 2007.
The ISC says it believes just under half of private schools offered the IGCSE in at least one subject.
But the vast majority of independent schools are still offering ordinary GCSEs, at least for most subjects.
Can pupils in state schools sit the IGCSE?
State school pupils do not sit the IGCSE currently because although they have been approved by Ofqual, the government has not approved them for state school funding.
Ofqual monitors qualifications in England on behalf of the government, working closely with its equivalents elsewhere in the UK.
It can approve qualifications, but it is up to England's Department for Children, Schools and Families to decide which it will fund state schools to offer.
State schools must adhere to the national curriculum, and given that the QCA raised concerns about the IGCSE in that respect, it seems unlikely the DCSF will change its stance.
The DCSF keeps a list of all qualifications it does fund, called the Section 96 List, and the IGCSE is not on it.
The Conservatives say the GCSE has been "devalued". They are urging the government to permit state schools to offer the IGCSE and "allow all students to take high quality international exams".
Isn't this adding to the "alphabet soup" of qualifications?
There are certainly more of them: Diplomas combining practical and theoretical learning are the latest to be made available.
Just to add to the confusion, one exam board syllabus calls the IGCSE by another name.
Two exam boards currently award it - Edexcel and the University of Cambridge International Exams.
Since the GCSE has to follow the national curriculum, and the international GCSE does not, the University of Cambridge International Exams has opted to call its version the "Cambridge International Certificate" instead.