Take deep breaths, maybe try meditation. Get some water Study prior to the exam Use coping mechanisms that work for you such as a a stress ball or a fidget Ask questions about the exam so you know how to prepare Ex. What kind of questions will be on the test? Maybe the teacher will say fill in the blank or multiple choice Be comfortable with the material ask teachers for help
Sorry if none of this works, these are just some things that help me before a exam.