Headteachers across England have warned of "unfair and unfathomable" A-level grades, with an estimated 40 per cent of entries given a lower grade than predicted.
In England, some 36 per cent of entries were reduced by one grade, while three per cent dropped by two due to the fact that exams across the UK were cancelled following the coronavirus pandemic.
In spite of this, overall results across England, Northern Ireland and Wales indicate a higher number of A* and A grades this session.
Geoff Barton, leader of ASCL head teachers’ union said: "While there has been an overall increase in top grades, we are very concerned that this disguises a great deal of volatility among the results at school and student level.
"We have received heartbreaking feedback from school leaders about grades being pulled down in a way that they feel to be utterly unfair and unfathomable. They are extremely concerned about the detrimental impact on their students."
The system assigning grades amid the pandemic has faced widespread criticism, with the Sixth Form Colleges Association referring to it as "flawed and unreliable". One third of college principals have said that results are lower or "dramatically lower" than in previous years.
An estimated 300,000 students will receive their results today, while Scottish students received theirs last week. Nicola Sturgeon has announced that pupils will be allowed to receive the grades predicted by teachers following considerable protests surrounding the current system.
Education Secretary Gavin Williamson has said the Westminster government will not follow suit.