Quintilian, Institutio Oratoria 1.8:
It was most excellently set down that a student’s reading should begin with Homer and Vergil, even though one needs a firmer judgment for understanding the virtues of those poets, for there will be time to develop it, since they will not be read just once. Meanwhile, the mind should rise up with the sublimity of heroic song, and it should raise the spirit with the greatness of the subject matter, and be filled with the finest examples. Tragedies are useful: even lyric poetry can afford some nourishment, if you make a careful selection not just of the authors but also of the parts of the work. For a lot of the Greek lyrics are licentiously written, and I would not really want some of the bawdier parts of Horace explained.
Ideoque optime institutum est ut ab Homero atque Vergilio lectio inciperet, quamquam ad intellegendas eorum virtutes firmiore iudicio opus est: sed huic rei superest tempus, neque enim semel legentur. Interim et sublimitate heroi carminis animus adsurgat et ex magnitudine rerum spiritum ducat et optimis inbuatur. VI. Vtiles tragoediae: alunt et lyrici, si tamen in iis non auctores modo sed etiam partes operis elegeris: nam et Graeci licenter multa et Horatium nolim in quibusdam interpretari.