A Level
There is a particularly big jump in academic rigour that occurs between GCSE and A Level maths. Even students who do exceptionally well at GCSE can sometimes find the change difficult (especially in the first year).
A Level maths introduces many new concepts not covered at GCSE, and also requires a mastery of algebra and other techniques which are fairly elementary up to year 11.
As with most A Levels, the expectation is for students to understand the material they are studying in greater depth, and to adopt self directed study, perhaps for the first time.
I offer 11 private maths tuition for the new A Level maths specification examined for the first time in 2019.
Whether a top grade is required to study a STEM subject at university, or a good grade is needed to enter the jobs market, I can help.
New A Level Curriculum
The government also made changes to A Level maths, although these changes were not as dramatic as those for GCSE. The most significant change are:

The modular system has been scrapped and the examination is now linear.

There is now a much bigger emphasis on mathematical modelling and problem solving.

AS Maths no longer counts towards A Level maths.

Mechanics and statistics are now both compulsory.
Modular Versus Linear
The introduction of the modular system in the past made A Level maths more accessible for some students, and so multiple retakes of specific modules are no longer possible.
Some teachers believe this change is better, as more time can be focused on teaching rather than constantly preparing for exams, whereas others feel the modular system was advantageous as terminal exams considerably raises the stakes (everyone can have a bad day!).
The absence of the modular system means keeping on top of the material throughout the two years is more important than ever, and having 11 maths tutor can help to ensure students do not fall behind.