So. I teach at a university and I do give an "assignment" exactly like this.

In a few of my classes, I have final projects that teams work on. I also have presentations. I used to require them of all students; and quickly learned this is a good way to waste valuable time.

Now, all my presentations are completely optional for NO CREDIT. You don't get penalized if you don't do them, and perhaps more importantly, I give ZERO EXTRA CREDIT for doing them.

As you can imagine, every single presentation I've gotten from this has been absolutely worth it.