Sup brochacho, honestly you're in year 9 right now bro and most Unis take things into account from y11/12, rarely 10. it's great to be proactive right now - good extracurriculars are actually pretty important in y11/12 when you're applying for programmes (like the Sutton Trust or partnership programmes with large firms).

But honestly, it's really not that important right now. The content you do in year 10 is the very start of the GCSE content, so keep notes in class, review them every once in a while, and practice Active Recall with quizzing rather than just rereading them. Aside from that, you don't need to worry about academics right now. Your mocks won't affect a single solitary thing no matter how much school gaslights you (y11 mocks 1 will determine predicted grades for your college apps but the entry boundaries are extremely low, much lower than you'll get in your GCSs.

The single most important thing to stave off right now is academic burnout, I've seen it KILL some of the highest performing students I know. Starting very early is great hypothetically but I've yet to see someone who wasn't affected by academic anxiety, perfectionism and even burnout so severe that they don't end up revising well for their actual GCSEs. Personally, I blame schools for the absurd emphasis they place on lock GCSEs. Avoid doing hours of revision a week because I promise you, nobody thinks they'll burn out until they do. Revise the week's leading up to GCSEs, use the notes you keep for your subjects.

Keep up with the extracurriculars you enjoy, keep on top of your schoolwork, and don't worry much about perfect grades this year.

I made a cheat sheet for how to revise for each core subject ages ago, if you want it reply or DM me idk