You can drop it yes, they can't force you to go to the lesson or to take the exam. Whether or not they let you take up another subject instead I can't say. What I can say is that, being a year 10, they are unlikely to want you to have gaps in your time table for malarky so, assuming you express very strongly your hate for fashion and assuming you are at least slightly good at 'getting what you want', it shouldn't be too difficult at all.