If I worked in a kindergarten,I would try my best to find something interesting to attract the students' (or rather,kids') attention,even if this means stopping the teaching and doing somethng else for a while.

If I worked in a primary school,I would probably scold the disobedient students directly and tell them that listening on class is one of the fundamental tasks for them in the next ten years or so,and that they have to form this habit.

If I worked in a high school,maybe I would ask these students to answer some questions,or maybe I could tell the whole class (in a louder voice) that what I would say next has direct relations with certain tests.

If I worked in a college,I would possibly do nothing to this phenomenon,as long as these students do not disturb others.

If I worked in a training agency,I would take a mixed approach between the ways for a kindergarten and for a college:neglecting their behaviors but trying to improve the attractivity of myself.