The school bell is an everyday sound from real schools, where an electric or hand-rung bell has long been used to mark lesson times, breaks and the end of the day. Online, the same ringing has become a shorthand for classroom life in memes, skits and short videos, because viewers recognise it instantly without any explanation. Creators reuse it to set a school setting in seconds, to signal a sudden change of scene, or to add a nostalgic touch to back-to-school content, which keeps it in regular use across social platforms.