GCSE and A-level students are being told their grades will be protected from Covid disruption, as exams get under way for most students in England, Wales and Northern Ireland.
Extra measures are in place to help pupils, but support varies across the different parts of the UK.
Covid led to an increase in top grades in 2020 and 2021, with results based on teacher assessments instead of exams.
England's exam regulator called this year a "step back to normal".
Unlike last year, students in England have not been given advance information about the topics they are likely to be tested on. Grades are expected to fall back in line with results in 2019.
However, some of the adjusted measures from last year remain in place.
Exams will be spaced apart more than they were prior to the pandemic, allowing for rest and revision.
