Does your teacher know about your stutter? If not, let him or her know, they'll most likely be fine with it. I had the same thing for my German class, the teacher let me go slow and ignored the stuttering since wasn't important. You're still fluent in English even though you stutter right? The same applies to French or anything else. If your teacher knows and says they'll lower your grade if you stutter, go talk to someone at your school, like an advisor or principal. It's horribly wrong of them to do so, because stuttering is a disability that instructors must accommodate for. I hope that helps, and good luck with the test!