School bells have long been used in real schools to mark the beginning and end of lessons, breaks and the school day, so the sound is instantly familiar to almost everyone who has attended school. Online, the same ringing has become a standard effect for classroom sketches, education videos, prank edits and reaction clips, where it sets the scene in a second. Its simple, unmistakable rhythm keeps it useful for creators who want a clear transition, a nostalgic cue or a comic signal that time is up.