England's exam authority awarded lower grades than teachers had predicted to almost 40 percent of pupils studying for their main school-leaving exams, results showed on Thursday, after the government cancelled the exams due to Covid-19.
Overall results were up on a year ago, but many teachers said their pupils had been unfairly treated while others raised concerns that the system adopted by the Ofqual exam board regulator favoured students at private schools.
The stakes are high for school leavers, whose places at the universities or training colleges of their choice hang on their grades.
Education minister Gavin Williamson defended the process and said he would not follow Scotland's lead in cancelling the results in favour of teachers' assessments. The Scottish government did so on Tuesday after a huge outcry.
"The majority of young people will have received a calculated grade today that enables them to progress to the destination they deserve," said Williamson, who had hastily introduced an appeals process on Wednesday after the Scottish debacle.
But Keir Starmer, leader of the opposition Labour Party, said the system had failed. "Something has obviously gone horribly wrong with this year's exam results," he said.
Other European countries have faced similar challenges. While students in Germany were able to sit their exams, France cancelled school-leaving exams but published methodology for awarding grades months in advance of results day.
In England, Ofqual awarded lower grades than teachers had estimated in 39 percent of cases, and higher grades 2 percent of the time.
Teachers estimated 14 percent of their pupils deserved the top 'A*' grade, almost twice the proportion who achieved this in exams last year. Ofqual called that "implausibly high".
But England's main teaching union criticised Ofqual's process, saying teachers knew their students better than any computer data prediction.
Ofqual said it tested its model to ensure it was fair to pupils of both genders and of different ethnic and social backgrounds.
However, it relied more heavily on teacher assessment for some subjects that attract low numbers of pupils - a process which critics said favoured pupils at private schools where some of those subjects are more common.
Under the last-minute changes announced on Wednesday, pupils unhappy with their grades will have avenues to appeal.