It is a qualification, it's just a little different to what it was before.
Why do a fourth AS and then drop it? Breadth. It's great if you don't know what route to go down. You can take 2 science subjects and 2 arts subjects, and you will drop one of them and can work towards a particular route.
So for me I do Maths, Biology, History and Politics. I'm either dropping History or Biology. Therefore at the end of Y13 I'll have either:
- Maths, Biology and Politics (prep for a science degree)
- Maths, Politics and History (prep for an arts degree)
It's also good if you know what you want to do but want to develop other skills. It's common to take Maths, two sciences and a humanity.