I couldn’t figure out a decent title for this thread but I know that a lot of students are advised to take A-level maths without it being made clear to them the lower the GCSE grade they have, the less likely they are to get good grades at A-level.
I think maths is the A-level that relies most on achievement at GCSE as it builds directly on the most difficult GCSE content.
Pearson have (very roughly) mapped their GCSE outcomes in 2017 to A-level outcomes in 2019 in the grid attached.
You can see from the mapping that students doing A-level with a grade 6 are most likely to get Ds and Es (and actually I would suspect that a lot of grade 6 students drop out before even taking the exam), and grade 7s are looking at Cs and Ds.
Obviously someone could work really hard, hit their stride and ace their A-level, or could peak at GCSE and struggle, but I think it’s worth having this info when deciding A-level choices.