honestly, if you were going to drop it after year 1 anyway it WILL NOT matter if you drop it now. I study biology currently (I am in A2 year) and although I enjoy it, it does get significantly harder from here on onwards. I got consistent C grades throughout the year and got a D in the AS so if you hate it and its taking time away from the subjects that you are going to use drop it. This will have no impact on uni entries particularly as next years AS students will only start with 3 subjects anyway.