What happens, in most cases, is that teachers get annoyed and frustrated with these students. In their enthusiasm to explain the material to the majority of students in class, teachers find the behaviour of this minority of students irritating, subversive and negative. Most often, they deal with them harshly and antagonistically and end up antagonising these students. Some of these students, as a result, may drop from the class, if they have the chance. More tolerance on the part of teachers.
Teachers have to guard against negative first reactions.
My first urge when I see a student whispering to a classmate or smiling when there is no reason to smile is to pause, look the student hard in the eye, and ask in the most condescending and authoritative tone possible why he or she is committing such an unjustified act. What I have learned to do over the years, however, is to totally suppress this first urge and show some tolerance. Students, teachers should tell themselves, are not their enemies. They do not hate them. Conduct business in class allowing students some space, some moments to goof off, whisper or smile.