Quintillian

A propos undervisning:

Let this first instruction be in the form of play; let the pupil be asked questions and praised for his answers, let him never rejoice in ignorance of anything: sometimes, when he will not learn, let another be taught of whom he may be jealous: let him compete sometimes with others and quite often think himself victorious: let him also be exited by rewards, which at that age are eagerly sought after.

– Quintillian: Institutio Oratoria I, 1, 20