Stop, stop, stop. You're going to take someone's eye out. Besides, you're saying it wrong. It's Levi-o-sa, not Leviosar.
One of a wizard's most rudimentary skills is levitation, the ability to make objects fly. Uh, do you all have your feathers? Good. Now, uh, don't forget the nice wrist movement we've been practicing, hmm? The swish and flick. Everyone.
Good. And enunciate. Wingardium Leviosa. Off you go then.
You do it then if you're so clever. Go on, go on.
Oh, well done! See here, everyone! Ms. Granger's done it! Oh, splendid!