You are still that bright scholarship student but you are just at a different junction in your learning curve.
I'm curious if you were fortunate enough to be boosted by a huge reservoir of pre learned knowledge and facts from your parents or others as you were growing up? This longer term knowledge bank is a massive benefit to gaining top marks on basic exam papers as your excellent pre knowledge would have put you head and shoulders ahead of other students?
Then comes a gap, where maybe you lost a year of knowledge layering? Year 9
Year 10 - Nothing has changed in your ability, but now you might find you need to really graft to get more new previously unknown facts on board for the memory recall. This is now a memory game (a bit like the memory capacity of a computer) Some knowledge is short term, some is longer term. You are probably learning new facts and new work every day. Have a look on this TSR site, and take advice for memory tips to recall facts. Go and speak to your tutors for their advice for exam technique and using old exam papers. Make sure you read exam questions carefully and use key words required in answers, answering questions effectively. Committing facts to memory is extremely hard work, and if you are memorising hard you will know about it! You have to keep repeating that learning and facts to commit them to memory. Sitting through interesting lectures is the easy part, like watching a show, but it doesn't necessarily help you to remember facts down the line.
So reassuring you - believe you are still right up there. Use TSR revision notes, and general revision advice. Get learning facts and use lots of different techniques to commit facts to memory (colours, pictures, songs, mnemonics etc, repetition, notes, scaffold notes) then use exam techniques to boost your offload of knowledge to answer questions effectively and well.
Giving up or easing up is not an option, get working. Never lose another day. Do the very best you can and then you can look back and say with hand on heart, I did my best and couldn't have done any more. The rest is fate and the questions that turn up on the day.
Wishing you all the best and I hope you get the grades you are striving for.