I would tell the professor beforehand, maybe at their office hours. Ask your professor if you can go first. You don’t want to be sitting and waiting letting the anxiety build. There is something to be said about tackling these fearful situations head on. It’s the difference between predator and prey. It changes your mindset. I would absolutely disclose to the class before your presentation. Disclosing that you are a person who stutters is a very powerful thing. It accomplishes several things: First, it takes pressure off of you to be fluent. Second, it lets the audience know what’s going on. Let’s face it, stuttering can sound weird sometimes. Usually people react poorly because they don’t know what’s going on or want to help but don’t know how. I would just say “Hey guys, I’m a person who stutters so you might hear me get stuck on my words sometimes but don’t worry I’m ok. Also, I’m feeling kind of nervous but I’ll give you my best.” With any luck you’ll stutter a little bit while saying that to break the ice. Try to smile and have fun, especially when you’re stuttering, it will put the audience at ease. Vulnerability is strength my friend, and it inspires people. The other students are nervous too and people love seeing other people overcome adversity. Think of The Voice or American Idol. People go crazy when some contestant with a tragic backstory overcomes all the odds to achieve success. In your case success does not equal fluency. Success is you facing these presentations head on. Good luck and let us know how it goes. Last tip: don’t address the audience as a whole, it can be overwhelming. Instead, make eye contact with a single person and talk to them, then switch. You’ll probably find someone that is looking back at you very attentive, maybe even smiling. Keep coming back to that person.