Applying to film schools is almost the same as applying to traditional four-year colleges. The difference lies in the application process itself. For example, most film school applications actually require interested students to submit a film that already has been made.
Why is this so often the case? Because film schools are extremely competitive and because those overseeing the applications process need a way to differentiate the cream of the crop from the junk. They generally require short films or have specific criteria that all prospective students must follow to form a valid application.
Because film schools rely on already-made films as a strong portion of the applications process, prospective students need to hone their crafts a bit before they ever set foot on campus. This separates the good from the bad. Therefore, it allows applications professionals to make stronger assessments of their future student bodies.