A Christmas Carol is one of those stories that makes the world seem snowy, full of lights, and tripping over with kindness. Maybe that's why this classic holiday story is a tale that teachers love to teach and movie directors love to adapt.
With over thirty serious adaptations of this Charles Dickens’s story (plus whatever production is afoot, about to be afoot, or just finishing up in your neck of the woods at present), A Christmas Carol is not going to take any of your students by surprise. Maybe they saw the Muppets' version, maybe they were in a play adaptation, or maybe they (or more likely their parents) are big fans of Scrooged. Whatever the source, all of your students are going to think that they know what happens in this story. Some might not even see the point in reading the original in its entirety.
But they definitely should. In discussing this novel, you might bring the adaptations into the equation to show them just how important reading the story front-to-back is. Show clips and compare it to the original text. Look at several versions of the same scene and see which one got closest to what Dickens intended. Don’t ignore their preconceived ideas. Embrace them.