Public speaking is about eliminating uncertainty. How long does it need to be? Is there to be a form of QA? Is it an open forum? Every choice in their presentation should be geared to meeting a need of the target audience (their class and instructor) with them in mind. Encourage them to roll with the mistakes made. Discourage stopping to, “restart”, share that it’s OK to mess up, forget things, but to ultimately move on and continue.
They must be fluent with their material. Practice it with you viewing and critique them. Get them used to being critiqued, adjust presentation based off of your input and practice it more. Add in distractions if time allows. As they gain precision, act out possible speed bumps. Anticipate, in order to eliminate uncertainty they may have. Elimination of uncertainty will yield confidence.
Most presenters will inherently always feel some level of nervousness regardless of preparation. Think sports, actors, it’s fine. Just try to eliminate what you can through all of the above information. There are a lot of great tips shared in this thread.