"Hugely worried" headteachers in England are bracing themselves for a turbulent end to the exam season, after warnings that an "unprecedented" raft of reforms could lead to "wild swings" in this year's results.
Exam boards and regulator Ofqual have advised parents and teachers to expect "volatility" in grades, particularly at GCSE, and school leaders are concerned that unexpected results could put their careers in jeopardy.
In a report published today, exam officers also warn of "burnout" among school staff struggling to contend with logistical difficulties and soaring stress levels, triggered by reforms designed to crack down on early and multiple GCSE entries.
The changes, introduced this year, included ending January and March sittings, switching to end-of-course assessment and discouraging resits by including only a student's first attempt at each exam in school league tables.
At GCSE, an increase in the number of pupils taking subjects such as history, geography and languages - a result of the introduction of the English Baccalaureate performance measure - could also "depress results", exam boards have warned.
Dame Joan McVittie, headteacher of Woodside High School in North London, said that schools had "absolutely no idea" what the impact of the "unprecedented" changes to qualifications would be.
"We're expecting a lot of turbulence," she said. "Headteachers are hugely worried about how much interference there has been by Ofqual in GCSEs this year. I fear there will no longer be a level playing field. As always, it's the children from the most deprived backgrounds who will suffer the most."
The Examination Officers' Association (EOA) has revealed that a quarter of the members it surveyed found the exam season more stressful than in previous years. Two-thirds (68 per cent) reported an increase in problems finding locations to sit exams, with 56 per cent struggling to get sufficient invigilators and 46 per cent contending with a rise in exam clashes.
The "burnout of exams staff is a growing concern", the EOA said, adding that a number of officers were being signed off sick because of stress during the exams.
Two-thirds (69 per cent) of exam officers reported an increase in students' requesting special access arrangements such as extra time, rest breaks and the use of laptops. Some attributed this to "pressure to perform in just one exam session with no opportunity to resit until the following year".
School leaders have also expressed concern that a repeat of the GCSE English grading problems of 2012, in which as many as 50,000 students were affected by a late change in grade boundaries, could put their jobs on the line.
"There's a real sense of uncertainty and apprehension," said Russell Hobby, general secretary of the NAHT headteachers' union. "Nobody knows what's going to happen. We hope there won't be any wild swings in the results of individual schools."
Robert Campbell, principal of Impington Village College in Cambridgeshire and a member of the Headteachers' Roundtable group of school leaders, said there was a mood of "anxiety" in many schools: "When you have Ofqual saying there will be some turbulence in the system, you have to batten down the hatches and prepare for some uncertainty.
"We don't know what to expect. Our predictions could be in the right ballpark, they might be 10 per cent one way or 10 per cent the other way. This turbulence is going to affect how schools fare in the accountability system. These are the sort of changes that can cost headteachers their jobs."
The Joint Council for Qualifications, which represents the main exam boards, will write an open letter to governors and parents on GCSE results day (21 August) to explain why grades might "look very different" from last year. Director general Michael Turner said: "At school level, it is reasonable to expect these changes to have varying degrees of impact and we may see volatility in the rank ordering of schools."
Some grade boundaries could be lowered to prevent students being "disadvantaged", Ofqual has admitted. Chief executive Glenys Stacey warned last week that the "totality" of the changes meant all schools were likely to be affected.
"Direct comparisons [with results from previous years] can't be made because you won't be comparing like with like," she said.
Geoff Barton, headteacher of King Edward VI School in Suffolk, said Ofqual had acknowledged that results could be narrowly interpreted by school governors and the media. "These conclusions can be used to trash the reputation of schools and, in too many instances, quietly dispense with headteachers who a year before were lauded as heroes," he warned.
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