How is the ability of an A Level cohort measured when determining grade boundaries?

As I understand it, this is one of the neglected factors that come to mind when we think about how grade boundaries are set. I was wondering how this is even determined? I would assume GCSE results but even then I can’t fully understand how it’s used. Especially for our cohort this year as we sat GCSEs with lenient grade boundaries back in 2022 and for last year who didn’t have a representative set of GCSEs.

Grade boundaries are decided on a National level. GCSE marks are irrelevant . All of the marks are looked at across the entire entry and the Chief examiner (in consultation with a team of senior examiners) decides where to set the boundary for each grade. So if a large number of candidates get a high mark, then the Grade A could be higher than last year. https://www.aqa.org.uk/exams-administration/results-days/grade-boundaries/standards/standards-over-time#:~:text=The%20experts%20look%20at%20marked,slightly%20lower%20than%20last%20year's.