I think the best thing to do is speak to your teachers before anything and check if a remark is worth it. In terms of carrying on with Computer Science, it's really a matter of what you want to study or what industry you'd want to work in the future. I'd say in this period of time, knowing a programming language is quite valuable in any industry so def. think about it. At the same time, if you want to go down a more sciencey route (like medicine), then keep phys, chem and math.