Institutio Oratoria

For with such a teacher their growth is stunted and their eyes are turned earthwards, and they are afraid to rise above the level of daily speech. Their leanness is regarded as a sign of health and their weakness as a sign of sound judgment, and while they are content that their work should be devoid of faults they fall into the fault of being devoid of merit. So let not the ripeness of vintage come too soon nor the must turn harsh while yet in the vat; thus it will last for years and mellow with age.

It is worth while too to warn the teacher that undue severity in correcting faults is liable at times to discourage a boy's mind from effort. He loses hope and gives way to vexation, then last of all comes to hate his work and fearing everything attempts nothing.