When it comes to letting teachers know, I'd suggest doing it BEFORE the first class if it's possible (I usually just send an email and say I'll follow up after class). I used to wait until the end of the first class and let them know afterward, but I recently switched because one of my teachers (I'm a college student) mocked my stutter in front of everyone on the first day of class, and everyone laughed lmao So consider doing that next time to prevent something like that from happening to you!