As with most things, some of the success (or failure) of a presentation lies in the design. Choose a topic that allows for students to communicate some sort of information about something that interests them - and what are teenagers interested in more than anything else? Themselves! This will automatically increase the engagement of your students during the creation of the presentation and during the presentations themselves.
From day one, try to provide students with an outline of the step-by-step process that they will be using to prepare for the presentation. Include on which days they will be working on the visual, brainstorming, practice, and anything else. This will allow them to see what you have in mind as well as what will be done in class versus at home. Breaking things into steps makes it far more manageable for students who may not have a lot of experience preparing presentations, let alone in another language.
After you explain the requirements of the oral presentation, model those requirements for your students by presenting to them. This allows them to see what your expectations are and also feel a sense of accomplishment when on day one they think....I can't do that...then a few days later they have done it! This will build their confidence and they will give you less grief over future presentations. This also gives your students a chance to learn more about you. If you want them to be comfortable putting information about themselves out there, you have to put yourself out there too!
If you want to make sure your students are successful, you need to plan structured, in class opportunities for practice. I like to move from individual practice, to partner practice, to small group practice - slowly increasing the size of the audience so that presenting in front of the entire class is not as much of a leap.
Have students keep track of their progress using a blank graph. If there are 10 things they need to be able to communicate, have them record how many of the 10 they can do successfully after each practice session. The graph will let them (and you) see their progress in a visual way. You can also use it to make decisions such as who will be ready to present on what day, who has already met the goal and can be pushed harder, and who is struggling and may need to simplify their presentation.
At first, they will whine - at least some of them. They will want to be allowed to have notecards when they present. Reading off notecards is reading, not speaking! They will want to come in and do the presentation privately in front of you, but this means that their classmates will not benefit from listening to and comprehending their presentation. Don't cave in! No notecards, and no private presentations without some sort of medical excuse. Many jobs require people to lead meetings, use video calling, and give presentations. It is our job to prepare them for this world.
If your students will be responsible for creating and showing a visual (which I highly recommend for EVERY presentation), you can save a LOT of time by having them use Google Drive to store their visual. You will greatly reduce the amount of time to find and load visuals between students and you will have access to go back and look at their visuals later. If you have them use Google Slides, the changes they make to the visual are saved automatically, so there are no "lost" visuals or files that magically get erased.
The day before presentations are to begin, I share a predetermined presentation order. Students who were present in class for each day of presentation preparation make the top of the list, followed by students who missed 1 day, 2 days, etc. However, I will always take volunteers first. On the day of the presentations I put a blank list on the board and students sign up to volunteer. Once I run out of volunteers, I resume the presentation order. This keeps things moving and allows students to have a little control over when they present.
It is no surprise that self-conscious teenagers aren't eager to jump up and speak in front of their peers. There are several things you can do to help your students be more comfortable while presenting to the class while still holding them to the standard. I allow my students to present from any location in the room as long as we can hear them clearly. They can sit at their desks, sit at my desk, stand in the back of the room, stand at the front of the room, sit on the back of the desk - wherever! When it comes down to it, I care that they speak and that the audience listens. As long as those two things are happening, where they are when it happens is their choice.
I don't know about you, but sometimes I feel like my brain is not what it used to be. I find that I am a much more accurate grader when I grade presentations immediately as they happen. When the student is presenting, I give them my full attention. Immediately upon their finishing (while the next student is preparing), I take out mu highlighter and highlight the ACTFL rubric with where they landed in each category and make small notes. I don't take the time to total the rubric, but I want my thoughts captured immediately. Some people like to videotape their students presenting so that they can go back and watch it again, but I find that that just leads me to second guess things which leads to inconsistencies.