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Thousands of teenagers across England, Wales and Northern Ireland are receiving their A-and AS-level results. But, in England, there have been changes to this year's A-level qualifications - the BBC News website sets out the changes.

What is different about this year's A-levels in England?

Under the new system, students sit all A-level exams at the end of two years of study, instead of taking modular exams throughout the course.

AS-level results no longer count towards A-level grades. No subject will have more than a 20% coursework component and most courses will be assessed entirely through exams.

Resits will still be available, but January exams will be scrapped, so students will have to wait until May/June of the following year for a chance to improve their grades.

Why was this change brought in?

The change was brought in by the former Education Secretary Michael Gove with the intention of making the exams more "fit for purpose" - or harder.

The new AS- and A-levels syllabuses have been phased in across schools in England from September 2015.

The DfE says: "The content for the new A-levels has been reviewed and updated. Universities played a greater role in this for the new qualifications than they did previously."

What is happening to AS-levels?

The AS-level is being decoupled from the A-level, which means it operates as a stand-alone qualification and the results do not count towards A-level grades - although in Wales and Northern Ireland, they will still count towards an overall A-level mark.

Provisional figures from the Department for Education show that the number of entries for AS subjects has fallen by 42% this summer.

Association of School and College Leaders general secretary Geoff Barton said it "sounded the death knell for AS-levels".

"The great benefit of the old system was that it gave students a broader range of knowledge and allowed them to keep their options open for longer," he said.

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"The decision to decouple these qualifications was an entirely unnecessary reform, which is narrowing the curriculum and reducing student choice."

Which subjects are being phased in when?

This year, new A-level qualifications were taken in:

art and design

biology

business

chemistry

computer science

economics

English language

English language and literature

English literature

history

physics

psychology

sociology

Next summer, candidates will sit the new A-level qualifications in the following subjects:

ancient languages (classical Greek, Latin)

dance

drama and theatre

geography

modern foreign languages (French, German, Spanish)

music

physical education

religious studies

In the summer of 2019, new exams will be sat in:

accounting

ancient history

ancient languages (biblical Hebrew A-level only)

classical civilisation

design and technology

electronics

environmental science

film studies

further mathematics

geology

government and politics

history of art (A-level only)

law

mathematics

media studies

modern foreign languages (Arabic, Bengali, Gujarati, Greek, Japanese, modern Hebrew, Panjabi, Persian, Polish, Portuguese, Turkish, Urdu)

modern foreign languages (Chinese, Italian, Russian)

music technology

philosophy

statistics

Hasn't all this change been stressful for the teenagers involved?

Young people and teachers have told the BBC that preparing for the new qualification has been stressful, especially as there were no past papers to refer to and some text books were written before some of the syllabuses were finalised.

Rosamund McNeil, from the National Union of Teachers, said: "The upheaval of a hastily reformed curriculum and the changes leading to a reduction in much of the coursework elements, created unnecessary stress and concern for pupils and teachers alike.

"While results nationally may have remained in line with those in the previous year, some schools and colleges will no doubt see considerable variation.

"The volatility around results and the accountability measures which use them can have damaging and unfair consequences."

What is happening elsewhere in the UK?

There have been no major changes in the other nations.

In Wales and Northern Ireland, AS-levels have remained as an integral part of studying for A-levels.

AS-levels contribute 40% of the total marks of the full A-level and can be taken at the end of the AS course or alongside A2.

In Scotland, students do not sit A-levels and AS-levels. Instead, they take Highers and Advanced Highers.

This year, the Higher pass rate dipped by 0.2%, but the total number of passes remained above 150,000 for a third successive year.

Reporting by BBC News education reporter Katherine Sellgren