How to get an A in chem, bio and psychology

Does anyone have any good tips to go from a C to an A in 4 months. I'm in year 12 and I've got my ucas exams in June ( I'm pretty sure) I've been trying to get help from school but it's not really going anything!! If it helps I'm pretty sure I've got good study habits, the problem is that im not retaining stuff for long periods of time. If it's not possible please just tell me. Thank you!!

What do you mean your UCAS exams . are you talking about your AS official exams in may I don’t think it’s June check again and does this result go towards your UCAS predicted grade for?or does your college do Jan mocks and bases on that ?
What did u get in ur GCSEs ?

Its what our predicted grades are based solely on and its definitely in June for me. My sixth forms quite strict about it so any mock exam grades won't be taken into consideration unfortunately. I mostly had 7s with a few 8s and 9s

Okay but just to confirm the official AS exams not past exams ? And what board do u do for psychology.

My school basically uses some sort of software system to create exam papers by combining previous a level questions, if that makes any sense??

Ahh I see our one is like official AS exams like grade boundaries but national level . Only grade goes up by A. Honestly I don’t known how your school will deal with grade boundaries but usually schools that do typically have a higher percentage of that in AS level exams.