GCSE pass rates in England, Wales and Northern Ireland have risen this year despite changes to make the exams more demanding.
The proportion of students achieving the pass levels - England's new grade 4 or grade C in Wales and Northern Ireland - has increased by 0.5% to 66.9%.
However, grades in Wales, a country which has also faced reforms, actually fell for a second year running. The proportion of students achieving A* to C grades decreased to 61.6%, whereas in Northern Ireland the proportion rose to 79.1%.
For the first time the majority of GCSEs in England are being graded from 9 to 1.
Roughly 4% of entries received grade 9, the highest grade, and 732 pupils achieved grade 9s in all of their subjects.
Girls continued to achieve better rates than boys - in terms of both the highest grades and the pass rate. However, the gap between the 2 genders narrowed this year with boys catching up.
In total, 17.2% of male's entries scored an A or a 7, an improvement on the 16.4% last year, whereas girls stayed at 23.7%.
Roughly 90% of entries in England this year were in the tougher form of GCSE, with more difficult content that is mostly graded on final exams, instead of coursework.
The aim is to pitch the exams at the standard of the highest-achieving countries in education, such as Finland and Singapore.
In Wales and Northern Ireland, pupils continue to receive results graded from A* to G.
20 of the most popular subjects at GCSE level in England have been graded in numerical format for the first time alongside English and maths, which were introduced in their new format last year. History, geography, the sciences and modern languages have all been transformed, with the intention of making them more difficult.
Of those achieving grade 9s and taking at least 7 of the new GCSEs, almost 2 thirds of them were girls. Only 732 of over half a million candidates achieved grade 9s in all their subjects.
Kevin Courtney of the National Education Union said 'success is being rationed', with fewer people achieving the new top grade compared with the previous A*.
Despite these alterations, exam regulators have tried to maintain stability with previous years, and stop a 'guinea pig' cohort from being disadvantaged.
This means that the overall pass rate - combining over 5 million entries in the 3 countries - has remained similar, up by 0.5% to 66.9% compared with the previous year.
The proportion of people achieving the equivalent of an A grade or higher - now grades 7, 8 and 9 - has also remained similar, at around 20%.
This has resulted in much better grade boundaries for some subjects. For one exam board, the grade 4 pass mark for maths was around 21%, for chemistry 26%, and biology 27%. Pupils had to score 42% to achieve the pass mark in English literature.
As long as teenagers are in full-time education in England, they must retake GCSE English and maths until they achieve at least a grade 4.
This year, 161,000 students aged 17 or older - likely to be candidates resitting - took maths at GCSE level and 149,000 English language. However of these, only 22.7% got a grade 4 in maths and 33.1% a 4 in English.
The private equity foundation, Impetus-PEF, claimed that thousands of young people were being let down, particularly those from disadvantaged backgrounds. Chief executive Andy Ratcliffe said that thousands of young people were 'stuck in an endless cycle of resits'.
The leader of the ASCL head teachers' union, Geoff Barton, said ' All the time and effort that has gone into reforming GCSEs, why have we done that? Because GCSEs were designed for an age when children were then maybe going into employment or going into the sixth form, so they were a gateway to other things.'
He further stated that 'Now everyone has to stay in education to 18, so why have we got children doing at least 30 hours of exams, all the stress and all the time and all the money that is, when actually for employers, it’s what they get at the age of 18 that’s going to be important. That’s where the real reform should be happening. And this is looking to me like a qualification that time forgot.'
He also claimed that there should be more of a focus placed on students achieving the lower grades. He said that 'Under the old GCSE, if you got an F or a G, whilst you may not have felt particularly pleased with it, there wasn't a national narrative saying 'you have failed to get the standard pass, you have failed to get a strong pass', yet that is now built in.'
He added that 'I just think we have to rethink what our education system is trying to do. If we had a more global outlook, our starting point would be, like all of those competitors of ours, what do we need to do so that those 11 years of teaching help every child to have something? It might not be a GCSE, but something. That's where the reform should have been.'
Sally Collier, head of the exam regulator Ofqual, stated that 'Students picking up their results today can be confident they have achieved the grades their performances deserve.'
School Standards Minister Nick Gibb said that 'Education standards are rising in our schools and pupils have shown their abilities by achieving excellent results today.'