It’s a useful plot point in movies or TV shows to have the main character transfer from one school to another or to have the protagonist befriend a new student. It’s also quite common for a group of friends just to ditch class for spurious reasons.
In real life, it’s not quite so easy to transfer schools at the drop of a hat, although it’s of course possible. Parents have to move jobs throughout the year, and their children need to find a new school. As for skipping class, anything’s possible, but there are definitely more consequences in real life than there are in the movies.