GCSE changes bring UK differences under devolution
Education Secretary Michael Gove's decision to change GCSEs in England means pupils around the UK could be sitting different versions of them.
From September, students starting GCSEs in England will take their exams at the end of their two-year courses.
At the moment, they can take GCSEs "in chunks" over two years - but Mr Gove believes this makes them less rigorous and narrows down what is studied.
But in Wales, schools will be able to choose between the two styles.
In Northern Ireland, no decision has been taken to change its system - which allows exams to be taken in either fashion - but an announcement is expected soon.
Pupils in Scotland mainly take Standard Grades although this system is due to be changed in 2014. A small number take GCSEs.
Mr Gove has pledged to improve the exam system in England.
He has said the trend for taking exams in modules - and for resits - has led to a downgrading of standards because it encourages teachers to "teach to the test" rather than give pupils broader knowledge of a subject.
Resits are also being limited under changes coming in from September.
Because power over education is devolved to the UK's nations, Mr Gove's decisions directly change only what happens in England, but indirectly, they may lead to changes elsewhere if the nations decide to follow suit.
This is what happened to an extent with tuition fees - after the decision was made to raise fees in England up to a maximum of £9,000, universities around the UK changed their fees for students from other parts of the UK.
A spokesman for the Department for Education said: "It's down to the Welsh and Northern Irish administrations to decide how to run their education systems - we do what we think best for English students.
"We make no apology for breaking the constant treadmill of exams and retakes throughout students' GCSE courses - school shouldn't be a dreary trudge from one test to the next. Sitting and passing modules has become the be-all and end-all, instead of achieving a real, lasting understanding and love of a subject.
"Students shouldn't be continually cramming to pass the next exam or resitting the same test again and again simply to boost their mark."
It will be the responsibility of the exams regulators of England, Wales and Northern Ireland to make sure GCSEs awarded in each nation are of an equal standard.
Jerry Jarvis, the former managing director of the Edexcel exam board, believes students stand to do better under a modular system - although he thinks the differences will be small.
"I would expect students taking modular exams to do better. Being able to take an exam in small chunks should in theory help someone to do better because of the revision," he said.
"It's not going to make a huge difference if you take advantage of the other things that contribute to improvement - for example teaching to the test, direct support that teachers are given."
Mr Jarvis, whose book Cheats, Choices and Dumbing Down was released recently, said: "Wales has its own [exams] authority and Northern Ireland too and as a consequence, inevitably, some variations are going to occur.
"As citizens of this country we move from region to region and in principle I don't think it's a great thing that there are regional differences."
The Welsh government has said schools in Wales can continue to enter pupils for modular exams and that some have already said they will continue to do so.
But it is looking at the issue in a review of qualifications which will report in November.
A spokesman said: "Ministers are committed to not making significant changes to GCSEs until after the outcomes of the Review of 14 to 19 Qualifications are known, unless urgent action is fully justified.
"However, where immediate action is felt necessary, we will take proportionate action."
Any decisions would be based on evidence, he said.
The Welsh exam board WJEC, whose exams are taken by students in England and Wales, is to produce both linear and modular GCSEs.
Last summer, it received about 350,000 exam entries from England.
Students from England will continue to be able to sit WJEC GCSEs - but only linear ones, taken after two years.
The board says it will maintain standards across both types of GCSE and has publishedguidance for schools.
A spokesman said: "The subject content will be the same for both linear and unitised options, ensuring consistency in the standards of the programmes of learning.
"We award all units on the basis of the standards of achievement expected from learners on completion of the course; the same standards are applied irrespective of when the units are taken."
Brian Lightman, the general secretary of the Association of School and College Leaders, says there is no evidence that linear exams are more rigorous than those taken in modules - and that schools in England should be free to choose which exams their pupils take.
"I suspect in Wales that most [head teachers] will carry on doing what they think is right for their students," he said.
"This is an imposed thing in England. We think it should be left as a choice."
Mr Lightman agreed there was a danger that some qualifications might be seen as better than others.
"It's a risk but we would just have to keep an eye on that. It's an opinion that the secretary of state has expressed but there is no evidence that a linear exam would be more rigorous than a modular exam. There are modular degrees after all - and even PhDs.
"The regulator will have to make sure they are similar."