Pressure is mounting on ministers to resolve the exam grades crisis with just days to go before GCSE results are published on Thursday.
They face calls to delay the results, change the grading algorithm or use the grades estimated by teachers, after complaints of unfair A-level results.
It comes as Northern Ireland said it would use teacher-assessed estimates for GCSE results this week.
The government has defended the approach it used to determine grades.
NI Education Minister Peter Weir said ahead of GCSE results day on Thursday it would scrap an algorithm that would have taken into account the past performance of schools.
Students across the UK were not able to sit exams as normal this year because of the coronavirus pandemic.
In England, 280,000 A-level results were downgraded from teacher’s predictions on Thursday, almost 40% of the total.
Exam regulator Ofqual has faced criticism over the statistical model it used to decide the grades.
Kate Green, Labour’s shadow education secretary, told BBC Breakfast: “We’re now going into week three of this debacle. We knew about the problem in Scotland two weeks ago, we know about the problem last week with A levels.
“Here we are just two or three days away from GCSE results and the government still hasn’t got a grip on the problem.”
Labour has called for teacher-assessed grades to be used for A-levels in England and has said the option should remain open for GCSEs if similar problems emerge.
Prime Minister Boris Johnson has been told by Labour leader Sir Keir Starmer that he needs to take “personal responsibility” and “fix” the situation.
Many students are expected to appeal, although there has been confusion over the appeals process after Ofqual withdrew its guidance for challenging results within hours of publishing it on Saturday.
New guidelines are still being drawn up by Ofqual, the Department for Education said on Sunday evening.
Meanwhile, hundreds of students held a demonstration in central London on Sunday to demand clarity over the appeals procedure.
The Sixth Form Colleges Association (SFCA) said it looked at 65,000 exam entries in 41 subjects from sixth form colleges and found that grades were 20% lower than historic performances for similar students in those colleges.
It said that this equated to “12,048 missing grades” in those colleges alone.
For example, in Biology, it found that 24% of sixth form college students were awarded a grade lower than similar students in recent years.
The SFCA said its analysis of 41 subjects had not found a single one where the results were above the three-year average.
Ofqual states that its objective for A-level results this year was to ensure “national results are broadly similar to previous years”.
SFCA said its research showed that Ofqual had “failed” to meet that “fundamental objective” and the model it used had “not only failed to produce broadly similar results, but has in fact produced worse results in every single subject”.
Bill Watkin, chief executive of the SFCA, said Ofqual should “immediately recalibrate and rerun the model to provide all students with an accurate grade”.
“Should this still fail to produce results that are broadly similar to previous years, students should be awarded the grades predicted by teachers (known as centre assessed grades),” he said.
Dr Mark Fenton, chief executive of the Grammar School Heads Association, said the results had also been unfair to some of its students.
He told the BBC that “a great injustice has been done” with “utterly baffling” results for some students.
He said the “only fair outcome” available would be to revert to the grade predicted by teachers and for the limit of 5% extra university places in England to be lifted.
The cap on increasing student numbers for each university was put in place by ministers to prevent academically selective universities recruiting heavily to make up for a fall in international students.
“Natural justice must surely now trump the understandable desire to maintain national standards in this, the most exceptional of years,” Dr Fenton added.
Three of Oxford University’s colleges – Worcester, Wadham and St Edmund Hall – have confirmed that all places offered to UK students will be secured irrespective of their A-level results.
After exams were cancelled due to the coronavirus pandemic, grades were awarded using a controversial modelling system, with the key factors being the ranking order of pupils and the previous exam results of schools and colleges.
Ahead of GCSE results due to be released on Thursday, former Conservative Education Secretary Lord Kenneth Baker urged the government to delay the publication of grades until the situation surrounding A-levels had been resolved.
“If you are in a hole, stop digging,” Lord Baker said.
The statistical model used by Ofqual faces two legal challenges, with students arguing they were unfairly judged on the school they attend.
Before results were released, the Department for Education announced a “triple-lock”, which meant that students could accept the grade calculated by Ofqual, appeal to receive a “valid mock result” or sit autumn exams.
The government announced on Friday that schools would not have to pay to appeal against exam grades.
In England, 36% of entries had grades lower than their teachers predicted and 3% were down two grades. A similar situation in Scotland saw a U-turn by the government, which agreed to accept teacher estimates of scores.
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