I’m curious how students have gotten high study scores for English... You could know a book back to front, but what about how you write your essays etc. ? What did you do? What recourses did you use to help you?
I would say it's important to understand what each essay section in the exam is looking for. You could summarise all your knowledge of a book in say, Section A and that would give you poor marks. Why it is important to essentially know a book back to front is to apply that knowledge to essay prompts and discussions.
Whilst practicing essays can be helpful, it isn't effective if you aimlessly write without addressing or breaking down the prompt you are writing about. So I think it's important to do a lot of planning! Personally, I didn't write many essays until the last few weeks before the exam, but instead I tried to find as many prompts as I could find for Sections A and B and brainstormed how I could explore that prompt in regards to the text/s. In terms of Section C, I would say it's less summarising what is said in the text, but identifying the impacts of certain tones/phrases/structure of the text on the reader/target audience. It's also crucial to get as much feedback as you can, just to target your specific weaknesses and make sure you're on the right track.
That's definitely not all the things you could do to achieve a high score (I certainly didn't get a 50) but that was just some of the things I did in English, as someone who started off as a relatively weak English student!