Hi I am currently taking Chem, Bio, Maths and French (looking to study Chem at uni) and in my opinion, 4 A-Levels is absolutely worth it if and only if you enjoy all 4 and are prepared to put the work in. For me french almost doesn't count as a fourth a-level because I am good at it and I really enjoy it, and it's so different to my other 3, so gives me a bit of break.
Art will eat up all your time. That's unavoidable.
I actually have friend who took Art, Bio and Chem and now she is wanting to study Chem at uni, she is really struggling to find unis that will accept these subjects without maths, so if you want to study chem, you will probably need maths.
If you want to study biology further, then just having chemistry as well is probably enough.
But if you want to take the science route later on then maths will be a huge asset. From replies further up though, I've seen that you're considering it due to your parents wanting you to do it, which will cause you more grief in the long run if you don't enjoy it yourself. A-level maths is hard, so enjoying it will mean it doesn't feel so bad.
An ideal solution would be to take all 4 to start and then drop one once you know a bit more about what you want to do, however idk if your school/ college would let you do this as some are stricter than others.
Whatever you choose, good luck from me!