I would love to take 3 a-levels since it would help me concentrate on 3 subjects (2 sciences, maths) but I'm sure what I will enjoy and what I will be good at. The fourth one is law which I want to take because first, (I think) I'll like the subject and second, I want to see what law is like because I'm considering law as a career. Yes, I know that law is not a requirement for law.
My plan is to take 4 a-levels and if I don't like a subject I'll drop it. Taking 4 AS though may affect my grades...