For GCSE I would make Maths, English Language, English Literature, Biology, Chemistry and Physics compulsory, and I'd encourage a language (e.g. French, German or Spanish) to be taken as well. Optional GCSE subjects would include PE, Music, Art, Textiles, History, Geography, Religious Studies and ICT. General PE lessons would also be optional, so students who would rather do homework or revision could do that instead (in a supervised classroom with a register though to avoid skiving). I would've loved that to have been the case when I was at school!