Anyone correct me if I’m wrong if they know more of the process but this is from what I remember
Grade boundaries are determined, from what I believe, a normal distribution process, meaning there’s roughly a set % of the population that can achieve certain grades. Don’t listen to rumours of people saying the boundaries are going to be lower. You’ll start to ease and up become complacent, which is what you don’t want (even if you tell yourself that, the brain is a mysterious thing and can do something that you don’t want to happen subconsciously).
Grades are determined by the performance of the cohort doing their tests. The better everyone does in the test, the higher the grade boundaries are typically. The worse everyone does on the test, the lower the boundaries. No one knows what the grade boundaries will be until the exams are over, not even the exam bodies themselves know what it will be (maybe roughly by looking at trends of data before).
Typically they are sort of similar to last years boundaries, minus/plus a 5-10 marks. I did watch an AQA video on grade boundaries back when I was doing GCSEs, and they follow a pattern where there’s a general rise in the boundaries (as teachers typically get better at teaching the content over time)
Hope this helps! Don’t listen to anyone about boundaries, focus on your own goals. There are some nasty people that try to fool others for their own benefit, don’t be a victim to this!