GCSEs in England have undergone the biggest shake-up for a generation.
As teenagers across the country prepare to get their results, here's everything you need to know about the exam reforms.
What has changed?
Under the new system, traditional A* to G grades will gradually be replaced with a 9 to 1 system, with 9 being the highest mark.
The first exams to be graded this way are English language, English literature and maths - core GCSEs taken by all teenagers.
A grade 7 is broadly equivalent to an A under the old system, while a 4 is broadly equivalent to a C.
The new courses feature much less coursework than the old GCSE qualifications, and modular courses - which saw pupils sit papers throughout their studies - have been scrapped in favour of "linear" GCSEs in which pupils take all of their exams at the end of the two-year course.
What about other subjects?
From summer 2018, sciences, history, geography and some modern languages will be tested under the new grading system.
Others such as art, music and drama will also be given grades for the first time next year.
A small number of other languages, taken by small numbers of students, will be first examined in 2020.
Are the new exams harder?
The new English and maths courses have more content and are tougher generally.
In maths, there is more content on topics such as number, ration and proportion, and pupils have to show clear mathematical arguments for their calculations and remember key formulae.
In English language, pupils now have to read a wider range of texts from different genres and time periods, and more importance is given to spelling, punctuation and grammar.
In English literature, students have to read a wide range of classic literature, including 19th century novels, Shakespeare and the Romantic poets.
Why has the system changed?
Education reforms in England began back in 2011, led by then Education Secretary Michael Gove.
A review of the national curriculum was announced first, with the overhaul of GCSEs starting in 2013.
Back in 2014, Mr Gove said the new tougher GCSE courses "set higher expectations", adding "they demand more from all students and specifically provide further challenge to those aiming to achieve top grades."
The Department for Education said that pupils who achieve a 4 in English and maths will not have to continue studying these subjects after the age of 16, in the same way that under the old system, those scoring at least a C did not have continue.
School performance tables will reflect schools' results in English and maths at grade 5s - considered a "strong" pass by the government.