Statistical standardisation is a huge problem at my school. We are a small school (abroad, if relevant, but the same sort of approach will apply to IGCSE as is outlined in this thread).
Our Y11 grades last year were APPALLING. The year before not great. This year, we happen to have a MUCH stronger cohort and we had new leadership 18 months ago who introduced a raft of academic changes that have benefited current Y11. But now their grades will effectively be pushed into line with the last few years'.
To put this into context -
We have averaged 1 A in English each year over the past three years. There are 2 students this year who should WALK an A and about 5 others who I would have comfortably predicted an A*.
Last year, almost the entire cohort failed to achieve a 4 in Maths. This year we had expected almost all students to achieve at least a 4.
The pattern continues across most subjects. We are looking into how we can express this clearly to the exam board, using mock exam data (v unreliable) and standardised testing e.g. Yellis scores. We don't have SATS.
Understandably the exam boards want to avoid grade inflation so if they are to allow us to push our grades up, they will need to push those of another school down. No school is going to admit that this year's cohort is significantly weaker than their norm!
Apologies if mixed grading causes confusion... We do some subjects using old grading system and some using new. It annoys us too!!