How I Use It
I always offer iMovie as an option for student projects. I require a script and give pretty strict planning guidelines in order to keep them focused on the goal of the project (as opposed to the blooper reel). I also give a tight schedule, defining the amount of time for filming and editing. I make it really clear that anything beyond the time allotted in class means time at home. Most students don't mind at all. Some prefer to focus on content rather than cinematography. For them, iMovie is not usually their medium (which is why I give choices).
iMovie is, as almost everyone knows, a movie editing application. As it has gone mobile (now part of iOs), it's even more useful for teachers because your students can use it on phones and iPads. It has gotten simpler to use over the years, and this is both curse and blessing. It's a good thing in that students can quickly become proficient at putting clips together, adding sound, and making a movie. It's a bad thing because it's become so drag-and-drop that many of my students seem to have less interest in exploring its 'reach'.