These individual instances are very few, probably, compared with the whole number of faults against which you ought to exert an influence.

And though you perhaps ought not to neglect those which may accidentally come under your notice, yet the observing and punishing such cases is a very small part of your duty.
You accidentally hear, I will suppose, as you are walking home from school, two of your boys in earnest conversation, and one of them uses profane language.

Now the course to be pursued in such a case is, most evidently, not to call the boy to you the next day and punish him, and there let the matter rest.

This would, perhaps, be better than nothing.
But the chief impression which it would make upon the individual and upon the other scholars would be, "I must take care how I _let the master hear me_ use such language again." A wise teacher, who takes enlarged and extended views of his duty in regard to the moral progress of his pupils, would act very differently.

He would look at the whole subject.