The key thing is what your Dc is capable of. Not everyone can get top GCSEs or get top A Level grades. However, it does make sense to choose A Levels that they can do really well in. It is a competitive world.
If your DC is capable of getting A* in some A Levels, the t hey should seriously consider those over those they would really struggle to get top grades in. And of course, GCSEs are a good predictor. Someone upthread mentioned a DC with a decent but not stellar GCSE maths GCSE who is now on for top grades at A Level. That is extremely extremely unusual..and actually, of course the grades are not achieved yet. In Maths of all subjects, doing A Level Maths without a 9 at GCSE, tends to have pretty poor outcomes at A Level. people are surprised by how bad - there are threads on MB devoted to it and statistics to show your likely A Level result being pretty low if you start with a 7 or 8. There is a massive step up and those getting a 7 or 8 have often achieved little more than half marks in their GCSE papers, so have lots of the GCSE topics they haven’t fully mastered and so will find A Level Maths extremely hard.
If you’re wanting to get A stars at A Level, you really ought to be achieving 8/9 at GCSE. It’s nit surprising there’s a strong correlation between GCSE success and A Level results when you think about it. Of course there are exceptions and some outperform what you’d expect..but remmeber for every anecdotal story, the vast majority don’t buck the normal trend.
It’s true that university offers don’t tend to require A star in any ir more than one subject, in the vast majority of places. People often mention Oxford making AAA the standard humanities offer. This is true, but the fact is that those making applications that are successful to get to interview or offer, will have nearly everyone with 3 x A star and very top GCSEs. You can see the statistics if you look at Oxford admissions reports. Very very few get offers based on less than stellar GCSEs or top A Level predictions unless they are flagged contextually for fairly significant issues which explain lesser achievement…and then of course they have to be superb in admissions tests and interviews. Oxbridge isn’t looking to admit those who’ve done pretty well, but those with tremendous potential and ability, even if the standard offer is actually very achievable.
Other top universities might ask for 1 x A star in a standard offer. But again, unless candidates have stellar GCSEs and top A Level predictions across the board, the offer itself might not be forthcoming.
But, most candidates aren’t applying to the most competitive courses at the very top institutions. Good Russel Group offers are available for those predicted As or a mix of As and Bs. Many of these students will have a mix of 6/7/8 type GCSEs.