My school requires a 6 in chem and a 6 in maths. I got those grades, but just about. So, I'm wondering if I might struggle in year 12. However, I am prepared to work really hard at it, even though it's not my strongest subject.
If you are interested in it, go for it. As long as you have a drive to do something you can excel at it. On the other hand, it is rather difficult to try as much with a subject you don't really like. I did AQA Chemistry at A-Level and I just did lots of questions and ended up doing well. Personally, I liked doing Chemistry at A-Level more than I did at GCSE.