The people of Canterbury have been so often reproved [scolded, criticized], (and frequently without a cause), for being dead and cold, that it has utterly discouraged them, and made them cold as stones. How delicate a thing is it to reprove! Tod do it well, requires more than human wisdom.
—John Wesley, Journal 3.348
Here Wesley points us to the danger of excessive and/or baseless criticism. There is a place for criticism among Christians because sometimes we err and need the benefit of loving criticism from a Christian friend who cares enough about us to want to help us. But the human tendency is to overdo things. We also forget that we too are fallible and not immune from criticism by others.
Excessive or baseless criticism will inevitably lead to a broken spirit and will usually produce contrary to that which we desire. Hence it should be used circumspectly and it should always be mixed with mercy and hope. If you feel the need to criticize a Christian brother or sister, ask God first to help you do so, and to remember that you are not superior to the one you criticize. Don’t be afraid to speak the truth in love, but be very afraid to criticize without warrant or in excess.
I feel that teachers also have to be careful in how they criticize. Of course, a student realizes a teacher is there to teach, as well as to correct and steer in the right direction. But teachers must still respect the “personn-ness” of their students. This is especially true in teaching children, who are just being formed.