Broken window phenomenon means that if the window of a house is broken, no one will repair it. Soon, other windows will be broken inexplicably. Therefore, if the bad phenomenon in the environment is allowed to exist, it will induce people to follow suit or even intensify.
According to the above definition, which of the following is not a broken window phenomenon?
In a classroom, two students spoke secretly. The teacher didn't stop them. Soon, most of the students in the class were chatting.