The head of one of England's biggest exam boards has apologised for marking errors which left hundreds of students with the wrong grades in their GCSEs and A-levels.
Andrew Hall, chief executive of the Assessment and Qualifications Alliance (AQA), admitted he was "concerned" that the problems could have affected students, particularly A-level candidates relying on grades for university places.
The exams regulator Ofqual has announced it has launched an inquiry into why around 600 GCSE, AS-level and A-level papers set by AQA were not fully marked.
Ofqual chief executive Isabel Nisbet said it is a "very serious matter".
"Ofqual is in full agreement with AQA that the first priority is to support students, schools and colleges," she said.
"AQA has assured us that they will make sure that the affected candidates are treated fairly and receive the marks their work merits as soon as possible. Once that is done, Ofqual's inquiry will focus on what went wrong and why it was not spotted sooner."
Around 150 A-level students are thought to have been given the wrong marks, along with 290 AS-level students and 190 GCSE students.
Mr Hall said he was concerned that grade changes could have affected the students, particularly A-level candidates who rely on grades for university places.
"I don't know what that one grade change has done, I'm concerned about it, yes," he said. "We want to do everything we can to help these students."
Earlier, Mr Hall said: "We are extremely sorry for any distress caused as a result of the original incomplete mark and are reviewing our processes to ensure there is no repeat of this error."
