Education policy in England requires full-time students aged 16–18 who have not achieved grade 4 or higher in GCSE Mathematics to continue studying maths.
Those who achieve grade 3 in GCSE Mathematics at age 16 are required to continue to study towards GCSE Mathematics post-16. Those who achieve GCSE grade 2 or below can either study towards resitting their GCSE or towards Functional Skills Maths level 2.

GCSE Mathematics Resit
Students are able to resit GCSE Mathematics following the same specifications as those taught in Years 10 and 11.
Pearson Edexcel has also created a specification for students studying GCSE maths post-16.
Functional Skills Maths
Functional Skills Maths for students who wish to achieve a level 1 or a level 2 in mathematics. Suitable for those who got a Grade 2 or lower at GCSE.
Level 1 – roughly equal to GCSE 2-3 in England and Wales, the old grade E-D in England and Wales, the current grade E-D in Northern Ireland or National 4 in Scotland.
Level 2 – roughly equal to GCSE grades 4 and above in England and Wales, the old grade C or above in England and Wales, the current grade C or above in Northern Ireland or above National 4 in Scotland.
Level 2 is offered as the following specifications:
City & Guilds Functional Skills Maths Level 2
AQA Functional Skills Mathematics
Future Quals Functional Skills Qualification in Mathematics (Reform)
Pearson Edexcel Functional Skills Mathematics (2019)
VTCT Skills Level 2 Functional Skills Qualification in Mathematic
Open Awards Level 2 Functional Skills Qualification in Mathematics
NOCN Functional Skills Qualification in Mathematics at Level 2
NCFE Level 2 Functional Skills Qualification in Mathematics
Highfield Functional Skills Qualification in Mathematics at Level 2 (Reformed)