The one thing many students overlook in A-level is Time. A lot of students I see lack the ability to finish the full paper on time, that is, in 2.5h, not 3h. We all need to check on the presentation and for silly careless mistakes.
The solution to this is old-school. You just have to sit down and train yourself to endure the full paper. This is very important as some students can’t even sit still for 2h without checking their handphone for updates. If you can, find a friend who is decently your standard and do the paper with him/her. Pace both of yourself together. But make sure you guys don’t cheat and consult each other. Some of my students know I simply do the paper alongside with them, analyse the paper alongside while doing it with them, highlighting the keywords that strike me when I read the questions. The worst was when I simply challenge them to do as fast as me.