I had a mild stutter throughout high school and even now in college. If it was a class that required speaking often or was talkative in nature, I would tell your teachers. In highschool, I usually only told my English, French(Canada), and Social Studies teachers that I stutter. Usually, they would have me present during lunch without an audience and refrain from asking me questions during class. And one of them even spoke with my mom so that they could arrange for me to get a speech therapist during school hours. Definitely worth it. During my later years of high school, I was able to do presentations and speeches in front of class from a lot of practice. I would change my speech so that I didn't have to say a certain word that I knew would induce my stutter.