Research on state dependent memory has shown that we are more likely to recall information if we are in a similar emotional state when we are encoding and retrieving the information. In other words - If you can replicate the testing environment in your studying environment then that should help you out. Since you are likely to be anxious when you are tested it is actually helpful to feel anxious when you are studying. There are of course limits, however and anxiety to the point of paralysis isn't so useful.

Where are you going to be tested? Are you able to study in a place that is similar to the place you are going to be tested in? I've had psychology lecturers say to me that they used to try and study in lecture theaters on weekends and in the evenings when there wasn't a class because it was most similar to where they were going to be tested. You don't need to obsess with the details of this (e.g., sitting in precisely the same room in precisely the same seat) but a general approximation should help.

Similarly, how are you going to be tested? Is it going to be multiple choice or is it going to be essay questions? Is the content you are tested on coming from lecture notes or a textbook or a combination of both? In studying for multiple choice I found it helpful to do my studying in the form of asking myself questions and then answering them. Trying to construct questions that could well appear on the exam. With essays I similarly tried to develop questions (and typically past years questions are available) and answer them in roughly the time I would have for the exam. Then develop them (with my notes) then try again (thus improving on the information I could recall).

One thing I did when my anxiety was at its worst... I discovered that a very small amount of chlorpromazine / largactal was enough to take the edge off it without dulling my brain. It actually improved my performance because I was able to think more fluently. It would be important to get the dosage right / know how it affects you well before the exams. It might be worth talking to a doc about this.

Otherwise... Mindfulness meditation / progressive muscle relaxation / aerobic exercise that gets endorphins pumping / enjoyable activities like walking or watching movies can help with anxiety. There might be classes at your school to help with managing anxiety. It is a fairly common problem. Good luck.