How can I ditch this fear?

When it comes to band, I am obsessed with the class. We have a playing test coming up. I am a percussionist and required to play a snare piece and mallet piece provided, both I have received. We go into a practice room with nothing but a recorder and are required to play both. My problem is when I go into the room I start getting panicky because of how quiet it is. This is 90% of our grade and determines our chair placements, I am more worried about my grade than anything.