GCSE students in England, Wales and Northern Ireland will receive their results on Thursday.

In England, GCSEs are graded using a numerical system from 9 to 1. Years ago, they were graded using an A-to-E letter system.

Exams are graded differently in Wales and Northern Ireland.

Scotland has a separate qualifications system to the rest of the UK, with no GCSEs.

The 9-1 grading scheme was brought in alongside an overhaul of the curriculum in England in 2014.

The rollout began in 2017 with three subjects – English language, English literature and maths – being the first to be graded in numbers. By 2020, all subjects were using the new grading system.

The highest grade is 9, while 1 is the lowest, and U means “ungraded”.

The number scale is not directly equivalent to the old letter one. However, the two scales do meet in certain places:

Grade boundaries dictate what the lowest mark is you can get to achieve a grade.

They are decided by examiners each year. Exam boards publish grade boundaries on results day.

Pupils need a 4 for a “standard pass” and 5 for a “strong pass”.

This means that a candidate who gets nine grade-4s has, technically, passed all their exams.

However, the government’s school league tables, external are based on the percentage of pupils who achieve a 5 or above in English and maths GCSEs.

Many sixth forms insist on a minimum number of 5s or 6s as a condition of entry for further study.

The numerical grading scheme was introduced as part of a 2014 curriculum overhaul by then-education secretary, Michael Gove.

It put less emphasis on GCSE coursework than before, with grades in almost all subjects decided in final exams.

The qualifications were designed to be more challenging, with exams taken after two years of study. Previously pupils covered the syllabus through a series of modules with regular assessments throughout the course.

At the time of the changes, the government argued that, external the new scale “recognises more clearly the achievements of high-attaining students, as the additional grades allow for greater differentiation”.

It also said that the move from letters to numbers would make it clear – for example to an employer – “whether a student has taken a new, more challenging GCSE, or an old reformed GCSE”.

Grades have changed in Northern Ireland too.

In summer 2019, the CCEA introduced a new nine-category grade scale – A* to G, including a C*.

Students may also get results with grades 9-1 if they take exams set by English boards.

The Welsh government introduced new and revised GCSE courses in September 2015.

The most significant changes were in English language, Welsh language and mathematics.

Wales retained the letter-based grading structure A*- G.