Of course you can improve!
If you study better, you will definitely raise your marks.
Do you:-make sure you learn and fully understand the content?
-memorise key definitions?
-do at least 3 practice tests on the subject? The more the better, often school exams may use questions from past papers from the HSC or other schools, has happened to me
-completely and fully understand each point in the syllubus?
-are confident you can answer ANY question the exam can throw at you?
If you answered 'yes' to all of the above, you should be able to ace your exam.
In the exam:
-make sure to stay calm, think you answer through before writing it down onto the paper
-check if it make sense and answers the question
-write as much as you know around what the question is asking about, so you have a greater chance of hitting the marking criteria. However, if the question asks for 2 points specifically, DO NOT write 3, they will only accept the first 2. Choose wisely
-if you have time, DEFINITELY go over your answers, I assure you that you will find at least one stupid mistake somewhere. Go back to the questions you weren't sure about, try them again. Then go through the multiple choice again (if there is one in the test), and by this I mean, do all of the questions AGAIN with greater depth, particularly those you weren't sure about during the test. Minimises any unnoticed errors.
Good luck!!!
Katya