I don't think your plan would cause any damage but I don't know that your body/Self will necessarily go along with your head plan, as you seem to already suspect might be a problem.

If I were you, I would design a stress/anxiety "course" for myself, maybe using a journal and workbooks, and just add it to your school work as another course, work an hour a day on it, etc. You could have assignments like greeting someone you don't know or smiling at someone in the hall and giving a little wave, etc., something a little difficult for you but not impossible. You could start a list of helpful/positive quotations, one a day, have projects like creating "games" to play with yourself (I once made a list of tasks I wanted to do, 20-30 (some duplicates, practice makes perfect), but which were scary/difficult in some way and put them on small slips of paper and folded them so I couldn't see what they were (think fortune cookie :-) and put one each in a plastic snack bag with a multi-vitamin and then drew one first thing in the morning, had the vitamin and then sometime during the day did the task.). Focusing on a task as a task instead of worrying about how I felt was very helpful and getting the tasks done gave me a better sense of self esteem and a bit of an "I can do this" momentum thing.

Anxiety is worry about the future and we cannot know the future. So, if we are going to think up what might happen why not think up positive ones instead of negative instead? If you can't think that someone you are waiting for who is late has stopped to buy you a present, that being too far-fetched then think up something funny or outrageous like animals from the zoo have gotten out and snarled traffic and they are having trouble catching them. People who are anxious like we are, if you think about it, have an excellent imagination! People who don't think up a million things that could go wrong, aren't going to be able to be very anxious, are they? LOL So use that wonderful imagination you have, embrace it (and remind yourself that is what is in play, not "reality" of what is wrong) and the anxiety will relax some and allow you to focus better on what you are doing or what is actually happening. Yes, you could flunk the test but you could also think up a really interesting sentence or idea while you are writing that essay answer that gets you excited about learning more and you forget to be anxious.