It depends on how you learn - for example, I am a crammer. I can cram an entire subject into 1-2 weeks, HOWEVER I made it easier on myself by understand content in class (understanding it at the time, not learning it).
If you are academic, you can cram easily. However if you struggle to aim above a D or C I assume education isn't really your thing. So my guess is that no, you won't be able to at least not with a lot of work. Cramming isn't just sitting and revising, the successful crammers have prepared material ready for a cram and understand how exam boards operate (so can quite accurately guess which topics to focus on). I got A*A*A a level and AA in AS levels via cramming (also waiting on an addition a level result in chemistry this year), but I prepared everything beforehand ready to just get in there a week before the exam. If you have only just realised you need to work, it'll be difficult.
My advice:
- Start immediately.
- Do a 'rough run' through all material, do 1-2 topics each subject per day. The rough run is to understand the material as you go through, not to try learn it off by heart.
- Once rouch run is complete, do at least another 2 runs of all material. The second should be learning off general concepts, god third should be picking up on that extra level of detail (learning all the little things you may have missed).
- Depending on time, another run can be very helpful. However if running shirt on time, start doing past papers ESPECIALLY for biology. Exam boards ask the same questions a lot just reworded, and knowing the exact wording of the answers off by heart means you can bang those marks out without much thought
- For biology, get your exam board textbooks. I took CCEA biology and just did an extra a level in chemistry, the CCEA big textbook was the only thing I used to learn the chemistry (that additional a level was via evening classes at a higher education college, so the quality of notes was awful. I only used the textbook). If there is anything similar available to you, I suggest you get it.
Good luck!