There were sighs of relief from students, teachers and education policymakers in England after the government’s long-awaited overhaul of GSCE exams passed off with few hitches and an upturn in the proportion of good grades.

Despite fears that tougher assessments in about 90% of exams would cause difficulties for some, results in England showed an increase in the proportion of 16-year-olds achieving a 4 or C and above to 69.2%, up from 68.7% last year.

The new assessments were designed to be more difficult. In most cases, they dispense with assessed coursework and rely on final exams, graded using a new scale from 9 to 1, which replaces the A* to G grades used since GCSEs were introduced 30 years ago.

The proportion of 16-year-olds attaining grade 7 or A and above rose from 20.9% last year to 21.4%, the highest level for seven years.

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“At the top end, it is much more demanding, and the purpose behind the introduction of the new grade scale is to create differentiation. The questions have been designed to be more demanding and stretching at the top end,” said Mark Bedlow, the head of the OCR examination board.

Pupils in England defied forecasts that the introduction of a more challenging top grade – 9 in the new system, requiring a higher mark than an A* – would severely limit the number of students gaining a clean sweep of top honours.

Instead, the exam regulator Ofqual said 732 students who took at least seven reformed GCSEs gained grade 9s in all of them. Schools around the country reported multiple cases of pupils winning nine, or even 10, grade 9s.

Among those who stood out, Freddie Mitchell, a pupil at Kingsdale foundation school in Southwark, south London, achieved 10 grade 9s, four A*s and a grade 8, which he intends to appeal against. Emma Beniston, of Rochester grammar school in Kent, also gained 10 of the new 9 grades along with two As in AS-level exams she took a year early.

But the tougher challenge for high achievers was counterbalanced by greater struggle for those at the other end of scale, especially those forced to resit maths and English under the government’s policy.

The GCSE results for 17-year-olds and over showed a big fall in the resit pass rate in maths, down from 26.5% last year to 23.7%, meaning 137,000 out of 180,000 entries resulted in failure.

Mark Dawe, the head of the Association of Employment and Learning Providers, said the compulsory resit policy was disgraceful and needed to be scrapped and replaced by functional skills tests for the workplace.

“We shouldn’t be subjecting tens of thousands of vulnerable young people to multiple failure and demotivating them for another couple of years. It’s time for the secretary of state to draw a line through this failed policy,” Dawe said.

Nick Gibb, the schools minister, congratulated students on their results and claimed that education standards were rising in England’s state schools “thanks to our reforms and the hard work of teachers”.

The new qualifications had some teething problems. Ofqual said it had intervened to rescue the efforts of more than 2,000 pupils taking the combined science qualification after their schools entered them for the wrong tier of the paper.

The upper tier of combined science was intended to grade those gaining a 4 or above, but uncertainty over which tier to enter resulted in some pupils struggling. They would have been failed but for Ofqual’s decision to award them a 3 instead.

Exam entry data revealed some schools in England were seeking to improve their league table performances by entering pupils a year earlier than normal. Data showed a near 30% increase in the number of 15-year-olds and younger being entered for English literature, part of a trend that is seeing some schools start GCSE courses at year nine or earlier.

Paul Whiteman, the head of the National Association of Head Teachers, said the government’s accountability measures were making schools rush pupils into taking early exams. “This is not a policy focused on what is right for students,” Whiteman said.

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The reformed exams in England appeared to favour boys, who made progress in catching up with the results achieved by girls. The effort was especially seen in chemistry, where the gap in the proportion of boys gaining grades 7 or higher shrank from seven percentage points to 1.6%.

But girls retained a clear advantage across the board and were responsible for more than 60% of the entries that gained the higher grade 9.

UK-wide figures for 16-year-olds showed the most improved performance for three years. In all subjects – including GCSEs in Wales and Northern Ireland which retain the A*-G grade – 21.5% of entries gained a grade 7 or A and above, compared with 21.1% last year. And 69.3% of entries gained grade 4 or C and above, compared with 68.9% last year.

In Wales, the exam regulator said this year’s results were difficult to compare with previous years, in part because of its own exam reforms.

“There has been a significant shift in the size and nature of the cohort taking GCSE exams this summer, as well as changes to many of the exams themselves, so it’s not possible to draw any firm conclusions,” said Philip Blaker, the chief executive of Qualifications Wales.

The proportion of candidates of all ages in Wales achieving A* to A rose to 18.5%, but the proportion gaining C or better fell for the second year in a row, to 61.6%.